TUOI C++

#include <bits/stdc++.h>
using namespace std;

int cha,con,x;
int main()
{
    freopen("tuoi.inp","r",stdin);
    freopen("tuoi.out","w",stdout);
    cin >> cha >> con;
    x=0;
    while(cha+x>2*(con+x)) 
        x++;
    cout << x; 
}