#include <iostream>
using namespace std;
int main(){
    int x,y,d;cin>>x>>y>>d;
    if(d < y){
        y = d;
    }
    if(d < x){
        x = d;
    }
    int ans = d+1;
    if(d > y){
        ans -= d-y;
    }
    if(d > x){
        ans -= d-x;
    }
    cout << max(0,ans) << endl;
}