poj 2924 Gauß in Elementary School

Gauß in Elementary School

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 7610		Accepted: 3440

Description

Johann Carl Friedrich Gauß (1777 – 1855) was one of the most important German mathematicians. For those of you who remember the Deutsche Mark, a picture of him was printed on the 10 – DM bill. In elementary school, his teacher J. G. Büttner tried to occupy the pupils by making them add up the integers from 1 to 100. The young Gauß surprised everybody by producing the correct answers (5050) within seconds.

Can you write a computer program that can compute such sums really quickly?

Given two integers n and m, you should compute the sum of all the integers from n to m. In other words, you should compute

Input

The first line contains the number of scenarios. Each scenario consists of a line containing the numbers n and m (−10⁹ ≤ n ≤ m ≤ 10⁹).

Output

The output for every scenario begins with a line containing “Scenario #i:”, where i is the number of the scenario starting at 1. Then print the sum of all integers from n to m. Terminate the output for the scenario with a blank line.

Sample Input

3
1 100
-11 10
-89173 938749341

Sample Output

Scenario #1:
5050

Scenario #2:
-11

Scenario #3:
440625159107385260

#include <iostream>
using namespace std;
int main ()
{
    int set,i;
    __int64 n,m;
    scanf("%d", &set);
    for(i=1;i<=set;i++) 
    {
        scanf("%I64d %I64d",&n,&m);
        printf("Scenario #%d:\n",i);
        printf("%I64d\n\n",(n+m)*(m-n+1)/2);
    }
    return 0;
}