#include<iostream>
using namespace std;

int main(){
    int a, b, s, ans;
    cin >> a >> b >> s;
    
    if(s == 1){
        ans = a;
        if(a == 0)  ans = 2;
    }else{
        if(abs(a-s) <= abs(b-s)){
            ans = abs(a-s) + s;
        }else{
            if(b < a)   ans = abs(b-s) + a-b + a;
            else        ans = b;
        }
    }

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