#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>
#include<limits>

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ll, string> pls;

int main()
{
	ll x, y, d;
	cin >> x >> y >> d;

	ll mx = max(x,y);
	ll mi = min(x, y);

	ll ans = 0;
	if (x + y < d)ans = 0;
	else {
		if (x < d)ans += d + 1 - x;
		if (y < d)ans += d + 1 - y;
		if (x >= d && y >= d)ans += d + 1;
	}
	cout << ans << endl;
	return	0;
}