Let us call a pair of integer numbers m-perfect, if at least one number in the pair is greater than or equal to m. Thus, the pairs (3, 3) and (0, 2) are 2-perfect while the pair (-1, 1) is not.

Two integers x, y are written on the blackboard. It is allowed to erase one of them and replace it with the sum of the numbers, (x + y).

What is the minimum number of such operations one has to perform in order to make the given pair of integers m-perfect?

Input

Single line of the input contains three integers x, y and m ( - 1018 ≤ x, y, m ≤ 1018).

Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preffered to use the cin, cout streams or the %I64d specifier.

Output

Print the minimum number of operations or "-1" (without quotes), if it is impossible to transform the given pair to the m-perfect one.

Examples

Input

1 2 5


Output

2


Input

-1 4 15


Output

4


Input

0 -1 5


Output

-1

Note

In the first sample the following sequence of operations is suitable: (1, 2) <image> (3, 2) <image> (5, 2).

In the second sample: (-1, 4) <image> (3, 4) <image> (7, 4) <image> (11, 4) <image> (15, 4).

Finally, in the third sample x, y cannot be made positive, hence there is no proper sequence of operations.
#include <bits/stdc++.h>
using namespace std;
const int inf = 1000000007;
const long long linf = 1000000000000000000LL;
const double eps = 0.000001;
const double pi = 3.14159265358979323846;
template <class T>
T abs(T k) {
  return k >= 0 ? k : -k;
}
template <class T>
T sqr(T n) {
  return n * n;
}
template <class T>
T gcd(T a, T b) {
  return b ? gcd(b, a % b) : a;
}
template <class T>
T mod(T a, T b) {
  return (a % b + b) % b;
}
template <class T>
T addmod(T a, T b, T c) {
  return (T)mod((long long)a + b, (long long)c);
}
template <class T>
T mulmod(T a, T b, T c) {
  return (T)mod((long long)a * b, (long long)c);
}
template <class T>
T powmod(T a, T b, T c) {
  return (T)(b ? mulmod(mod((T)sqr((long long)powmod(a, b >> 1, c)), c),
                        b & 1 ? a : 1, c)
               : 1);
}
template <class T>
void maxe(T &a, T b) {
  a = max(a, b);
}
template <class T>
void mine(T &a, T b) {
  a = min(a, b);
}
template <class T>
void mode(T &a, T b) {
  a = mod(a, b);
}
template <class T>
void addmode(T &a, T b, T c) {
  a = addmod(a, b, c);
}
template <class T>
void mulmode(T &a, T b, T c) {
  a = mulmod(a, b, c);
}
template <class T>
void powmode(T &a, T b, T c) {
  a = powmod(a, b, c);
}
void fileio_in_out() {
  freopen(".in", "r", stdin);
  freopen(".out", "w", stdout);
}
void fileio_txt() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
}
const int N = 1111111;
int test;
long long n, m, k, ans;
long long dfs(long long x, long long y) {
  if (x >= k || y >= k) return 0;
  if (x < y) swap(x, y);
  long long ret = 0;
  if (y >= 0) {
    ret = 1;
    y += x;
  } else {
    ret = (-y) / x;
    y += ret * x;
    if (y < 0) {
      ret++;
      y += x;
    }
  }
  return ret + dfs(x, y);
}
long long getans() {
  if (n >= k || m >= k) return 0;
  if (n <= 0 && m <= 0) return -1;
  return dfs(n, m);
}
int main() {
  scanf("%I64d%I64d%I64d", &n, &m, &k);
  printf("%I64d\n", getans());
  return 0;
}
