#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1e9;
int MOD = 1e9+7;
main(){
    int x,y,d;
    cin >> x >> y >> d;
    int cnt = min(x,y);
    if(d < min(x,y) || d > max(x,y)){
        cnt -= min(abs(min(x,y)-d),abs(max(x,y)-d));
    }
    if(cnt < 0)cnt = 0;
    else cnt++;
    cout << cnt << endl;
}