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

ll solve(ll x, ll y, ll d){
    ll yt = min(d, y);
    ll xs = d - yt;
    ll xt = min(d, x);
    
    return max(0ll, xt - xs + 1);
}

int main(){
    ll x, y, d;
    cin >> x >> y >> d;
    
    cout << solve(x, y, d) << endl;
    return 0;
}