#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <algorithm>
#include <numeric>
#include <functional>
#include <set>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cctype>
#include <climits>
#include <fstream>
#include <bitset>
#include <time.h>

#define ll long long
#define FOR(i,a,b) for(int i= (a); i<((int)b); ++i)
#define RFOR(i,a) for(int i=(a); i >= 0; --i)
#define FOE(i,a) for(auto i : a)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define DUMP(x)  cerr << #x << " = " << (x) << endl;
#define SUM(x) std::accumulate(ALL(x), 0LL)
#define EPS 1e-14

using namespace std;


int main(int argc, char *argv[]) {
    int x, y, d;
    cin >> x >> y >> d;

    int ans = 0;
    FOR(i, 0, d + 1) {
        int j = d - i;
        ans += 0 <= i && i <= y && 0 <= j && j <= x;
    }
    cout << ans << endl;
    
    return 0;
}