#include <bits/stdc++.h>
#define REP(a,b,c) for(int a=b; a<(int)c; a++)
#define rep(a,b) REP(a,0,b)
typedef long long int llint;
using namespace std;

int main(){
  int A, B, S;
  cin >> A >> B >> S;
  int ans;
  if(S==1){
	if(A==0) ans = 2;
	else ans = A;
  }
  else if(abs(A-S) <= abs(B-S)){
	//A come
	ans = abs(A-S) + S;
  }else{
	//B come
	ans = abs(B-S);
	if(A<S) ans += B-A + A;
	else if((A-S) < (S-1)) ans +=  A-S + A;
	else ans += A + S-1;				 
  }

  cout << ans << endl;;
  return 0;
}