2

#include<stdio.h>
int main()
{
    long long int a,b,temp,c,d,sum;
    while(scanf("%lld%lld",&a,&b)!=EOF){
        if (a>b){
            temp=a;
            a=b;
            b=temp;
        }
        a=a-1;
        c=(a*(a+1))/2;
        d=(b*(b+1))/2;
        sum=d-c;
        printf("Sum of %lld to %lld is -> %lld;\n", a+1,b,sum);
    }
    return 0;

}