#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

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

    long long a = 0, b = 0;
    if ( d >= x ) {
        a = d - x;
    }
    if ( d >= y ) {
        b = d - y;
    }
    cout << max( 0LL, d + 1 - (a + b) ) << endl;

    return 0;
}