#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int x,y,d;
  cin>>x>>y>>d;
  if(x+y<d) return cout<<0<<endl,0;
  Int p=max(0LL,d-y),q=min(x,d);
  cout<<q-p+1<<endl;
  return 0;
}