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 double EPS = 0.0000001;
const double PI = acos(-1);
const long long INFLL = 0x7FFFFFFFFFFFFFFF;
const int INF = 0x7FFFFFFF;
template <typename T>
inline void next(T &num) {
  char c;
  num = 0;
  do {
    c = getchar_unlocked();
  } while (c != EOF && c == ' ' && c == '\n' && c == '\t');
  int sign = (c == '-' ? -1 : 1);
  if (c != '-') num += (c - '0');
  while ((c = getchar_unlocked()) != EOF && c != '\n' && c != '\t' &&
         c != ' ') {
    num *= 10;
    num += (c - '0');
  }
  num *= sign;
}
inline string getstr() {
  string str;
  char k;
  while ((k = getchar_unlocked()) == ' ' || k == '\n') {
    k = getchar_unlocked();
    if (k == ' ' || k == '\n')
      continue;
    else
      break;
  }
  str.push_back(k);
  while ((k = getchar_unlocked()) != EOF && k != '\n' && k != '\t' &&
         k != '\v' && k != '\0' && k != ' ')
    str.push_back(k);
  return str;
}
long long x, y, m;
int main() {
  next(x);
  next(y);
  next(m);
  if (m < 0) {
    if (x >= m || y >= m)
      puts("0");
    else
      puts("-1");
    return 0;
  }
  if (x < m && y < m) {
    if (x > 0 || y > 0) {
      if (x < y) swap(x, y);
      long long res = 0;
      if (y < 0) {
        res += abs(y / x);
        y %= x;
        if (y < 0) {
          y += x;
          res++;
        }
      }
      while (x < m && y < m) {
        x += y;
        y = x - y;
        res++;
      }
      printf("%I64d\n", res);
    } else
      printf("-1\n");
  } else
    puts("0");
  return 0;
}
