Problem - 1001_Sum Problem

Sum Problem

Time Limit: 1000/500 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)

Total Submission(s): 297065    Accepted Submission(s): 74177

Problem Description

Hey, welcome to HDOJ(Hangzhou Dianzi University Online Judge).

In this problem, your task is to calculate SUM(n) = 1 + 2 + 3 + ... + n.

 

Input

The input will consist of a series of integers n, one integer per line.

 

Output

For each case, output SUM(n) in one line, followed by a blank line. You may assume the result will be in the range of 32-bit signed integer.

 

Sample Input

1100

 

Sample Output

15050

 

Author

DOOM III

 

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#include<stdio.h>int main(){    int n;    while(scanf("%d",&n)!=EOF){        printf("%d\n\n",(int)((1+n)*0.5*n));    }    return 0;}