#include <bits/stdc++.h>   using namespace std;   long long x, y, m;   int main() {     cin >> x >> y >> m;     if (x >= m || y >= m)       cout << 0 <<   n ;     else {       if (x <= 0 && y <= 0)         cout << -1 <<   n ;       else {         long long cc = 0;         if (x > y) swap(x, y);         if (x < 0) {           cc += x >= 0 ? x : -x / y;           x += y * (long long)cc;         }         while (x < m && y < m) {           if (x < y)             x = x + y;           else             y = x + y;           cc++;         }         cout << cc <<   n ;       }     }   }   