Sum Problem
Time Limit: 1000/500 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 486843 Accepted Submission(s): 123616
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.
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
1
100
100
Sample Output
1
5050
5050
Author
DOOM III
AC 代码：
#include < iostream >
using namespace std;
typedef long long LL;
int main()
{
LL a,b;
while(cin>>a)
{
cout<<(a+1)*a/2<<endl;
cout<<endl;
}
return 0;
}
