Ural 1068 sum

A -
Sum(1.5.1)
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Time Limit:2000MS    
Memory Limit:65536KB     64bit IO Format:%I64d & %I64u

Description

Your task is to find the sum of all integer numbers lying between 1 and
N inclusive.

Input

The input consists of a single integer N that is not greater than 10000 by it's absolute value.

Output

Write a single integer number that is the sum of all integer numbers lying between 1 and
N inclusive.

Sample Input

input	output
-3	-5

题目大意：

求出1到N的和

#include <iostream>
using namespace std;
int main()
{
int n;
cin>>n;
int sum=0;
int i;
if(n<1)
for(i=n;i<=1;i++)
sum=sum+i;
if(n>=1)
for(i=1;i<=n;i++)
sum=sum+i;
cout<<sum<<endl;
return 0;
}