1

#include<iostream>
#include<stdio.h>
using namespace std;
int main()
{
    long long int a,b,sum1,sum2,temp;
    while(scanf("%lld %lld",&a,&b)!=EOF)
    {
        if(a<b)
        {
            temp = a-1;
            sum1 = (b*(b+1)/2);
            sum2 = (temp*(temp+1)/2);
            printf("Sum of %lld to %lld is -> %lld;\n",a,b,sum1-sum2);

        }
        else
        {
            temp = b-1;
            sum1 = (a*(a+1)/2);

            sum2 = (temp*(temp+1)/2);
            printf("Sum of %lld to %lld is -> %lld;\n",a,b,sum1-sum2);


        }
    }
    return 0;
}