Let's denote a function 

<image>

You are given an array a consisting of n integers. You have to calculate the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Input

The first line contains one integer n (1 ≤ n ≤ 200000) — the number of elements in a.

The second line contains n integers a1, a2, ..., an (1 ≤ ai ≤ 109) — elements of the array. 

Output

Print one integer — the sum of d(ai, aj) over all pairs (i, j) such that 1 ≤ i ≤ j ≤ n.

Examples

Input

5
1 2 3 1 3


Output

4


Input

4
6 6 5 5


Output

0


Input

4
6 6 4 4


Output

-8

Note

In the first example:

  1. d(a1, a2) = 0; 
  2. d(a1, a3) = 2; 
  3. d(a1, a4) = 0; 
  4. d(a1, a5) = 2; 
  5. d(a2, a3) = 0; 
  6. d(a2, a4) = 0; 
  7. d(a2, a5) = 0; 
  8. d(a3, a4) = - 2; 
  9. d(a3, a5) = 0; 
  10. d(a4, a5) = 2. 
#include <bits/stdc++.h>
using namespace std;
const long long BASE_DIGITS = 9;
const long long BASE = 1000000000;
struct Bint {
  long long sign;
  vector<long long> a;
  Bint() : sign(1) {}
  Bint(long long v) { *this = v; }
  Bint &operator=(long long v) {
    sign = 1;
    if (v < 0) {
      sign = -1;
      v = -v;
    }
    a.clear();
    for (; v > 0; v = v / BASE) a.push_back(v % BASE);
    return *this;
  }
  Bint(const string &s) { read(s); }
  void read(const string &s) {
    sign = 1;
    a.clear();
    long long pos = 0;
    while (pos < (long long)s.size() && (s[pos] == '-' || s[pos] == '+')) {
      if (s[pos] == '-') sign = -sign;
      ++pos;
    }
    for (long long i = s.size() - 1; i >= pos; i -= BASE_DIGITS) {
      long long x = 0;
      for (long long j = max(pos, i - BASE_DIGITS + 1); j <= i; j++)
        x = x * 10 + s[j] - '0';
      a.push_back(x);
    }
    trim();
  }
  friend istream &operator>>(istream &stream, Bint &v) {
    string s;
    stream >> s;
    v.read(s);
    return stream;
  }
  friend ostream &operator<<(ostream &stream, const Bint &v) {
    if (v.sign == -1 && !v.isZero()) stream << '-';
    stream << (v.a.empty() ? 0 : v.a.back());
    for (long long i = (long long)v.a.size() - 2; i >= 0; --i)
      stream << setw(BASE_DIGITS) << setfill('0') << v.a[i];
    return stream;
  }
  bool operator<(const Bint &v) const {
    if (sign != v.sign) return sign < v.sign;
    if (a.size() != v.a.size()) return a.size() * sign < v.a.size() * v.sign;
    for (long long i = ((long long)a.size()) - 1; i >= 0; i--)
      if (a[i] != v.a[i]) return a[i] * sign < v.a[i] * sign;
    return false;
  }
  bool operator>(const Bint &v) const { return v < *this; }
  bool operator<=(const Bint &v) const { return !(v < *this); }
  bool operator>=(const Bint &v) const { return !(*this < v); }
  bool operator==(const Bint &v) const { return !(*this < v) && !(v < *this); }
  bool operator!=(const Bint &v) const { return *this < v || v < *this; }
  friend long long __compare_abs(const Bint &x, const Bint &y) {
    if (x.a.size() != y.a.size()) {
      return x.a.size() < y.a.size() ? -1 : 1;
    }
    for (long long i = ((long long)x.a.size()) - 1; i >= 0; --i) {
      if (x.a[i] != y.a[i]) {
        return x.a[i] < y.a[i] ? -1 : 1;
      }
    }
    return 0;
  }
  Bint operator-() const {
    Bint res = *this;
    if (isZero()) return res;
    res.sign = -sign;
    return res;
  }
  void __internal_add(const Bint &v) {
    if (a.size() < v.a.size()) {
      a.resize(v.a.size(), 0);
    }
    for (long long i = 0, carry = 0;
         i < (long long)max(a.size(), v.a.size()) || carry; ++i) {
      if (i == (long long)a.size()) a.push_back(0);
      a[i] += carry + (i < (long long)v.a.size() ? v.a[i] : 0);
      carry = a[i] >= BASE;
      if (carry) a[i] -= BASE;
    }
  }
  void __internal_sub(const Bint &v) {
    for (long long i = 0, carry = 0; i < (long long)v.a.size() || carry; ++i) {
      a[i] -= carry + (i < (long long)v.a.size() ? v.a[i] : 0);
      carry = a[i] < 0;
      if (carry) a[i] += BASE;
    }
    this->trim();
  }
  Bint operator+=(const Bint &v) {
    if (sign == v.sign) {
      __internal_add(v);
    } else {
      if (__compare_abs(*this, v) >= 0) {
        __internal_sub(v);
      } else {
        Bint vv = v;
        swap(*this, vv);
        __internal_sub(vv);
      }
    }
    return *this;
  }
  Bint operator-=(const Bint &v) {
    if (sign == v.sign) {
      if (__compare_abs(*this, v) >= 0) {
        __internal_sub(v);
      } else {
        Bint vv = v;
        swap(*this, vv);
        __internal_sub(vv);
        this->sign = -this->sign;
      }
    } else {
      __internal_add(v);
    }
    return *this;
  }
  template <typename L, typename R>
  typename std::enable_if<std::is_convertible<L, Bint>::value &&
                              std::is_convertible<R, Bint>::value &&
                              std::is_lvalue_reference<R &&>::value,
                          Bint>::type friend
  operator+(L &&l, R &&r) {
    Bint result(std::forward<L>(l));
    result += r;
    return result;
  }
  template <typename L, typename R>
  typename std::enable_if<std::is_convertible<L, Bint>::value &&
                              std::is_convertible<R, Bint>::value &&
                              std::is_rvalue_reference<R &&>::value,
                          Bint>::type friend
  operator+(L &&l, R &&r) {
    Bint result(std::move(r));
    result += l;
    return result;
  }
  template <typename L, typename R>
  typename std::enable_if<std::is_convertible<L, Bint>::value &&
                              std::is_convertible<R, Bint>::value,
                          Bint>::type friend
  operator-(L &&l, R &&r) {
    Bint result(std::forward<L>(l));
    result -= r;
    return result;
  }
  friend pair<Bint, Bint> divmod(const Bint &a1, const Bint &b1) {
    assert(b1 > 0);
    long long norm = BASE / (b1.a.back() + 1);
    Bint a = a1.abs() * norm;
    Bint b = b1.abs() * norm;
    Bint q = 0, r = 0;
    q.a.resize(a.a.size());
    for (long long i = a.a.size() - 1; i >= 0; i--) {
      r *= BASE;
      r += a.a[i];
      long long s1 = r.a.size() <= b.a.size() ? 0 : r.a[b.a.size()];
      long long s2 = r.a.size() <= b.a.size() - 1 ? 0 : r.a[b.a.size() - 1];
      long long d = ((long long)BASE * s1 + s2) / b.a.back();
      r -= b * d;
      while (r < 0) {
        r += b, --d;
      }
      q.a[i] = d;
    }
    q.sign = a1.sign * b1.sign;
    r.sign = a1.sign;
    q.trim();
    r.trim();
    auto res = make_pair(q, r / norm);
    if (res.second < 0) res.second += b1;
    return res;
  }
  Bint operator/(const Bint &v) const { return divmod(*this, v).first; }
  Bint operator%(const Bint &v) const { return divmod(*this, v).second; }
  void operator/=(long long v) {
    assert(v > 0);
    if (llabs(v) >= BASE) {
      *this /= Bint(v);
      return;
    }
    if (v < 0) sign = -sign, v = -v;
    for (long long i = (long long)a.size() - 1, rem = 0; i >= 0; --i) {
      long long cur = a[i] + rem * (long long)BASE;
      a[i] = (long long)(cur / v);
      rem = (long long)(cur % v);
    }
    trim();
  }
  Bint operator/(long long v) const {
    assert(v > 0);
    if (llabs(v) >= BASE) {
      return *this / Bint(v);
    }
    Bint res = *this;
    res /= v;
    return res;
  }
  void operator/=(const Bint &v) { *this = *this / v; }
  long long operator%(long long v) const {
    assert(v > 0);
    assert(v < BASE);
    long long m = 0;
    for (long long i = a.size() - 1; i >= 0; --i)
      m = (a[i] + m * (long long)BASE) % v;
    return m * sign;
  }
  void operator*=(long long v) {
    if (llabs(v) >= BASE) {
      *this *= Bint(v);
      return;
    }
    if (v < 0) sign = -sign, v = -v;
    for (long long i = 0, carry = 0; i < (long long)a.size() || carry; ++i) {
      if (i == (long long)a.size()) a.push_back(0);
      long long cur = a[i] * (long long)v + carry;
      carry = (long long)(cur / BASE);
      a[i] = (long long)(cur % BASE);
    }
    trim();
  }
  Bint operator*(long long v) const {
    if (llabs(v) >= BASE) {
      return *this * Bint(v);
    }
    Bint res = *this;
    res *= v;
    return res;
  }
  static vector<long long> convert_base(const vector<long long> &a,
                                        long long old_digits,
                                        long long new_digits) {
    vector<long long> p(max(old_digits, new_digits) + 1);
    p[0] = 1;
    for (long long i = 1; i < (long long)p.size(); i++) p[i] = p[i - 1] * 10;
    vector<long long> res;
    long long cur = 0;
    long long cur_digits = 0;
    for (long long i = 0; i < (long long)a.size(); i++) {
      cur += a[i] * p[cur_digits];
      cur_digits += old_digits;
      while (cur_digits >= new_digits) {
        res.push_back((long long)(cur % p[new_digits]));
        cur /= p[new_digits];
        cur_digits -= new_digits;
      }
    }
    res.push_back((long long)cur);
    while (!res.empty() && !res.back()) res.pop_back();
    return res;
  }
  void fft(vector<complex<double> > &a, bool invert) const {
    long long n = (long long)a.size();
    for (long long i = 1, j = 0; i < n; ++i) {
      long long bit = n >> 1;
      for (; j >= bit; bit >>= 1) j -= bit;
      j += bit;
      if (i < j) swap(a[i], a[j]);
    }
    for (long long len = 2; len <= n; len <<= 1) {
      double ang = 2 * 3.14159265358979323846 / len * (invert ? -1 : 1);
      complex<double> wlen(cos(ang), sin(ang));
      for (long long i = 0; i < n; i += len) {
        complex<double> w(1);
        for (long long j = 0; j < len / 2; ++j) {
          complex<double> u = a[i + j];
          complex<double> v = a[i + j + len / 2] * w;
          a[i + j] = u + v;
          a[i + j + len / 2] = u - v;
          w *= wlen;
        }
      }
    }
    if (invert)
      for (long long i = 0; i < n; ++i) a[i] /= n;
  }
  void multiply_fft(const vector<long long> &a, const vector<long long> &b,
                    vector<long long> &res) const {
    vector<complex<double> > fa(a.begin(), a.end());
    vector<complex<double> > fb(b.begin(), b.end());
    long long n = 1;
    while (n < (long long)max(a.size(), b.size())) n <<= 1;
    n <<= 1;
    fa.resize(n);
    fb.resize(n);
    fft(fa, false);
    fft(fb, false);
    for (long long i = 0; i < n; ++i) fa[i] *= fb[i];
    fft(fa, true);
    res.resize(n);
    long long carry = 0;
    for (long long i = 0; i < n; ++i) {
      long long t = (long long)(fa[i].real() + 0.5) + carry;
      carry = t / 1000;
      res[i] = t % 1000;
    }
  }
  Bint mul_simple(const Bint &v) const {
    Bint res;
    res.sign = sign * v.sign;
    res.a.resize(a.size() + v.a.size());
    for (long long i = 0; i < (long long)a.size(); ++i)
      if (a[i])
        for (long long j = 0, carry = 0; j < (long long)v.a.size() || carry;
             ++j) {
          long long cur =
              res.a[i + j] +
              (long long)a[i] * (j < (long long)v.a.size() ? v.a[j] : 0) +
              carry;
          carry = (long long)(cur / BASE);
          res.a[i + j] = (long long)(cur % BASE);
        }
    res.trim();
    return res;
  }
  static vector<long long> karatsubaMultiply(const vector<long long> &a,
                                             const vector<long long> &b) {
    long long n = a.size();
    vector<long long> res(n + n);
    if (n <= 32) {
      for (long long i = 0; i < n; i++)
        for (long long j = 0; j < n; j++) res[i + j] += a[i] * b[j];
      return res;
    }
    long long k = n >> 1;
    vector<long long> a1(a.begin(), a.begin() + k);
    vector<long long> a2(a.begin() + k, a.end());
    vector<long long> b1(b.begin(), b.begin() + k);
    vector<long long> b2(b.begin() + k, b.end());
    vector<long long> a1b1 = karatsubaMultiply(a1, b1);
    vector<long long> a2b2 = karatsubaMultiply(a2, b2);
    for (long long i = 0; i < k; i++) a2[i] += a1[i];
    for (long long i = 0; i < k; i++) b2[i] += b1[i];
    vector<long long> r = karatsubaMultiply(a2, b2);
    for (long long i = 0; i < (long long)a1b1.size(); i++) r[i] -= a1b1[i];
    for (long long i = 0; i < (long long)a2b2.size(); i++) r[i] -= a2b2[i];
    for (long long i = 0; i < (long long)r.size(); i++) res[i + k] += r[i];
    for (long long i = 0; i < (long long)a1b1.size(); i++) res[i] += a1b1[i];
    for (long long i = 0; i < (long long)a2b2.size(); i++)
      res[i + n] += a2b2[i];
    return res;
  }
  Bint mul_karatsuba(const Bint &v) const {
    vector<long long> a6 = convert_base(this->a, BASE_DIGITS, 6);
    vector<long long> b6 = convert_base(v.a, BASE_DIGITS, 6);
    vector<long long> a(a6.begin(), a6.end());
    vector<long long> b(b6.begin(), b6.end());
    while (a.size() < b.size()) a.push_back(0);
    while (b.size() < a.size()) b.push_back(0);
    while (a.size() & (a.size() - 1)) a.push_back(0), b.push_back(0);
    vector<long long> c = karatsubaMultiply(a, b);
    Bint res;
    res.sign = sign * v.sign;
    long long carry = 0;
    for (long long i = 0; i < (long long)c.size(); i++) {
      long long cur = c[i] + carry;
      res.a.push_back((long long)(cur % 1000000));
      carry = cur / 1000000;
    }
    res.a = convert_base(res.a, 6, BASE_DIGITS);
    res.trim();
    return res;
  }
  void operator*=(const Bint &v) { *this = *this * v; }
  Bint operator*(const Bint &v) const {
    if (a.size() * v.a.size() <= 1000111) return mul_simple(v);
    if (a.size() > 500111 || v.a.size() > 500111) return mul_fft(v);
    return mul_karatsuba(v);
  }
  Bint mul_fft(const Bint &v) const {
    Bint res;
    res.sign = sign * v.sign;
    multiply_fft(convert_base(a, BASE_DIGITS, 3),
                 convert_base(v.a, BASE_DIGITS, 3), res.a);
    res.a = convert_base(res.a, 3, BASE_DIGITS);
    res.trim();
    return res;
  }
  Bint abs() const {
    Bint res = *this;
    res.sign *= res.sign;
    return res;
  }
  void trim() {
    while (!a.empty() && !a.back()) a.pop_back();
    if (a.empty()) sign = 1;
  }
  bool isZero() const { return a.empty() || (a.size() == 1 && !a[0]); }
  friend Bint gcd(const Bint &a, const Bint &b) {
    return b.isZero() ? a : gcd(b, a % b);
  }
  friend Bint lcm(const Bint &a, const Bint &b) { return a / gcd(a, b) * b; }
  friend Bint sqrt(const Bint &a1) {
    Bint a = a1;
    while (a.a.empty() || a.a.size() % 2 == 1) a.a.push_back(0);
    long long n = a.a.size();
    long long firstDigit =
        (long long)sqrt((double)a.a[n - 1] * BASE + a.a[n - 2]);
    long long norm = BASE / (firstDigit + 1);
    a *= norm;
    a *= norm;
    while (a.a.empty() || a.a.size() % 2 == 1) a.a.push_back(0);
    Bint r = (long long)a.a[n - 1] * BASE + a.a[n - 2];
    firstDigit = (long long)sqrt((double)a.a[n - 1] * BASE + a.a[n - 2]);
    long long q = firstDigit;
    Bint res;
    for (long long j = n / 2 - 1; j >= 0; j--) {
      for (;; --q) {
        Bint r1 =
            (r - (res * 2 * Bint(BASE) + q) * q) * Bint(BASE) * Bint(BASE) +
            (j > 0 ? (long long)a.a[2 * j - 1] * BASE + a.a[2 * j - 2] : 0);
        if (r1 >= 0) {
          r = r1;
          break;
        }
      }
      res *= BASE;
      res += q;
      if (j > 0) {
        long long d1 =
            res.a.size() + 2 < r.a.size() ? r.a[res.a.size() + 2] : 0;
        long long d2 =
            res.a.size() + 1 < r.a.size() ? r.a[res.a.size() + 1] : 0;
        long long d3 = res.a.size() < r.a.size() ? r.a[res.a.size()] : 0;
        q = ((long long)d1 * BASE * BASE + (long long)d2 * BASE + d3) /
            (firstDigit * 2);
      }
    }
    res.trim();
    return res / norm;
  }
};
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long N;
  cin >> N;
  map<long long, long long> mp;
  long long sum = 0;
  Bint res = 0;
  for (long long i = 1; i <= N; i++) {
    long long n;
    cin >> n;
    res += n * (i - 1 - mp[n] - mp[n - 1] - mp[n + 1]) -
           (sum - mp[n] * (n)-mp[n - 1] * (n - 1) - mp[n + 1] * (n + 1));
    sum += n;
    mp[n]++;
  }
  cout << res << '\n';
  return 0;
}
