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

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