//
//  main.cpp
//  Q310
//
//  Created by AkihiroKOBAYASHI on 7/13/15.
//  Copyright (c) 2015 Akhr5884. All rights reserved.
//

#include <iostream>

int main(int argc, const char * argv[]) {
    
    int x, y, d, value, xtemp, ytemp;
    value = 0;
    xtemp = 0;
    
    std::cin >> x >> y >> d;
    
    if(x+y < d) {
        value = 0;
    }
    else {
        while(x >= xtemp) {
            ytemp = d - xtemp;
            if(ytemp >=0 && ytemp <= y) {
                value++;
            }
            xtemp++;
        }
        
    }
    
    std::cout << value << "\n";
    return 0;
}