#include <bits/stdc++.h>
using namespace std;

int main(){
    int x,y,d;
    cin>>x>>y>>d;
    if(x<y){
        swap(x,y);
    }
    if(d<=y){
        cout<<d+1<<endl;
    }else if(d>x+y){
        cout<<0<<endl;
    }else if(d>x){
        cout<<x+y+1-d<<endl;
    }else{
        cout<<y+1<<endl;
    }
}