#include <iostream>
using namespace std;
int main(){
	int x,y,d;	cin>>x>>y>>d;
	int cnt=0;
	for(int i=d-y>=0?d-y:0;i<x;i++){
		if(i<=d&&d-i<=y) cnt++;
	}
	cout<<cnt<<endl;
	return 0;
}