1001

Sum Problem

Problem Description
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.//只有无符号的需要显式定义，如果没有unsigned 标识，就是有符号的。

Sample Input
1
100
Sample Output
1

5050
Author

DOOM III

#include <iostream>using namespace std;int main(){int a,n;while(cin>>a){int i=0;while(a){i=i+a;//i为从1到a的和a--;}cout<<i<<endl;cout<<endl;}return 0;}