#include <iostream>
#include <cmath>

using namespace std;
int main(void)
{
	int A,B,S,s;
	cin >> A >> B >> S;
	
	if(abs(S-A)<=abs(S-B))
	{
		s = 2*S-A;
	}else
	{
		s=A+B-1;
	}
	if(S!=0 && s==0)
	{
		s =2*S+A;
	}
	cout << s << endl;
}