#include<iostream>
#include<vector>
#include<string>
#include<cmath>
#define rep(i,a) for(int i = 0 ; i < a ; i ++)
#define loop(i,a,b) for(int i = a ; i < b ; i ++)
using namespace std;
int main(void){
  int x,y,d;
  cin>>x>>y>>d;
  int res = 0;
  rep(i,x+1){
    rep(j,y+1){
      if(i+j==d){
//        cout<<i<<j<<endl;
        res++;
      }
    }
  }
  cout<<res<<endl;
}