#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000

long long get(long long n){
	if(n<0)return 0;
	return n+1;
}

int main(){
	
	long long x,y,d;
	cin>>x>>y>>d;
	
	long long ans = get(d);
	ans -= get(d-(x+1));
	ans -= get(d-(y+1));
	ans += get(d-(x+y+2));
	
	cout<<ans<<endl;
	
	return 0;
}