#include <bits/stdc++.h>
#define MOD 1000000007

using namespace std;

typedef pair<int,int> P;
typedef pair<int,pair<int,int>> PP;
typedef long long LL;

const double EPS = 1e-8;
const int INF = 1e9;

int dy[] = {0,1,0,-1};
int dx[] = {1,0,-1,0};

int main(void) {
	int x,y,d;
	cin >> x >> y >> d;
	if(x+y < d){
		cout << 0 << endl;
		return 0;
	}
	
	int tmp = 0;
	if(x < d) tmp += d-x;
	if(y < d) tmp += d-y;
	cout << d+1-tmp << endl;

	return 0;
}