typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;

int main() {
    ld x,y,h;
    std::cin >> x>>y>>h;
    h/= 1000.0;
    ll r= 1e18;
    ll l= -1;
    
    while(r-l>1){
        ll mid = (r+l)/2;
        
        ll tmpa = ((1-mid)*log(2)-log(h)+log(x))/log(2)-0.0001;
        ll tmpb = ((1-mid)*log(2)-log(h)+log(y))/log(2)-0.0001;
        // std::cout << ((1-mid)*log(2)-log(h)+log(y))/log(2) << std::endl;
        // std::cout << tmpa<<" "<<tmpb<<" "<<mid << std::endl;
        if(tmpa+tmpb>=mid-1){
            l = mid;
        }else{
            r = mid;
        }
    }
    
    std::cout << l+1 << std::endl;
}