#include<iostream>
#include<string>
#include<vector>
#include<set>
using namespace std;


int main(){
  int x,y,d;
  cin >> x >> y >>d;
  if(x+y<d){
      cout<<0<<endl;
      return 0;
  }else{
      int min,max;
      min = y>=d ? 0 : d-y;
      max = x>=d ? d : x;
      cout<<max-min+1<<endl;
  }
    return 0;
}