#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 A, B, S;
	cin >> A >> B >> S;

	ll ans = 0;
	if (S <= A ||((A == B) && A > S)) {
		ans = A;
	}
	else if (B > S && S > A) {
		ans = min(B,((S - A) * 2)+A);
		if (A == 0)ans++;
	}
	else if (S > A && A >= B) {
		ans = (S - A) + S;
		if (A == 0)ans++;
	}
	else if (S > B && B > A) {
		ans = 2 * S - B;
		if (A == 0)ans++;
	}
	else if (S == B && S > A) {
		ans = (S-A)*2 + A;
	}
	cout << ans << endl;
	return	0;
}