#include <bits/stdc++.h>
#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;


int main(){
    int x, y, d, min1 = -1, max1 = 1e9 + 1;
    cin >> x >> y >> d;
    min1 = min(x, y);
    max1 = max(x, y);
    if (d <= min1) cout << d + 1 << endl;
    else if (min1 < d && d <= max1) cout << min1 + 1 << endl;
    else if (max1 < d && d <= max1 + min1) cout << max1 + min1 - d << endl;
    else cout << 0 << endl;
}