#include <bits/stdc++.h>   using namespace std;   int main() {     long long int a, b, c;     cin >> a >> b >> c;     if (a >= c || b >= c) {       cout <<  0 ;     } else if (a <= 0 && b <= 0) {       cout <<  -1 ;     } else {       long long int count = 0;       while (a < c && b < c) {         if (a > b) {           swap(a, b);         } else if (a < 0) {           count += (abs(a) / b + (abs(a) % b != 0));           if (abs(a) % b) {             long long int r = abs(a) % b;             a = (b - r);           } else {             a = 0;           }         } else {           long long int p = b;           b += a;           a = p;           count++;         }       }       cout << count;     }   }   