#include<iostream>
#include<fstream>
using namespace std;
ifstream fin("animal.in");
ofstream fout("animal.out");

long long br = 0;
int dyn[1002][1002];

void Rec(int a, int b, int c) {
    if (b >= a) return ;
    if (c < 0) return ;
    if (dyn[a][b] == 1) return ;
    br++;
    dyn[a][b] = 1;
    Rec(a + 1, b, c - 1);
    Rec(a, b + 1, c - 1);
    return ;
}

int main() {
    int a, b, c;
    fin >> a >> b >> c;
    if (b >= a) {
        int raz = b - a + 1;
        c -= raz;
        a += raz;
    }
    if (a + b != 0 && c >= 0) br++;
    Rec(a + 1, b, c - 1);
    Rec(a, b + 1, c - 1);
    fout << br;
    return 0;
}