#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("Yes");}else{puts("No");}
#define MAX_N 200005

int main() {
    ll x,y,d;
    cin >> x >> y >> d;

    ll ans = 0;

    if(x + y >= d){
        if(y >= d){
            ans = min(x,d) + 1;
        }else{
            ans = x + 1 - (d - y);
        }
    }

    cout << ans << endl;
    return 0;
}