#include<bits/stdc++.h>
#define int unsigned long long
using namespace std;

signed main(){
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int a, b, c;
    cin >> a >> b >> c;
    int l = -1;
    int r = 3e18;
    while(l + 1 < r){
        int m = (l + r) / 2;
        int sr = 2 * a + b * 3 + c * 4 + m * 5;
        int z = a + b + c + m;
        if(z * 3.5 <= sr){
            r = m;
        }
        else{
            l = m;
        }
    }
    cout << r;
    return 0;
}