318C - Perfect Pair - CodeForces Solution

#include <bits/stdc++.h>

using x64 = long long;

int main() {
    x64 x, y, m;
    std::cin >> x >> y >> m;

    if (x > y) std::swap(x, y);

    if (y >= m) {
        std::cout << 0 << std::endl;
    }
    else {
        if (y <= 0) {
            std::cout << -1 << std::endl;
        }
        else {
            x64 ctr = 0;
            if (x < 0) {
                ctr = (-x + y - 1) / y;
                x += ctr * y;
            }
            while (y < m) {
                x += y;
                if (x > y) std::swap(x, y);
                ctr++;
            }
            std::cout << ctr << std::endl;
        }
    }
}