#include <stdio.h>

int main(void) 
{
	int a,b,start,end,n,sum=0;
	scanf("%d",&a);
	scanf("%d",&b);
	if(a>b)
	{
		start=b;
		end=a;
	}else{
		start=a;
		end=b;
	}
	for(n=start;n<=end;n++)
	{
		sum +=n;
	}
	printf("%d",sum);
    return 0;
}