#include <iostream>
using namespace std;

int summa(int a, int b) 
{
	if (a==b) return b;
	else return a+summa(a+1,b);
}

int main()
{
	int a,b;
	cin>>a;
	cin>>b;
	if(a>b){
		std::swap(a,b);
	}
	cout<<summa(a,b);

	return 0;
}