#include <iostream>
using namespace std;

int main(){
	int x,y,d,count;
	cin>>x>>y>>d;

	for (int i = 0; i < x+1; ++i)
	{
		for (int j = 0; j < y+1; ++j)
		{
			if (i+j == d)
			{
				count++;
			}
		}
	}
	cout<<count<<endl;
	return 0;
}