Sir Kindly Tell me the why my this Problem's solution is not acceptable?
#include<iostream>
using namespace std;
int main()
{

    int num,n;
    int i;
    cin>>n;
    while(n>0)
    {
        cin>>num;
        if(num>10000)
            return 0;
        else if(num<0)
        {
            i = ((num*(num-1))/2)*(-1);
            cout<<i+1<<endl;
        }
        else
        cout<<(num*(num+1))/2<<endl;
        n--;
    }
    return 0;
}

You have to read/write a single number.

But Sir when i was taking a single input then at that time also not accept my solution.
The error was "wrong answer Test#2".
Kindly tell me what was wrong that time?

Well, obviously you have an incorrect formula
Did you made a check on the paper with, let's say N = -1?
The "i = ((num*(num-1))/2)*(-1); cout<<i+1<<endl;" formula is wrong also for the sample input, you will output 7.

No sir when i give input N=-1 the OutPut is 0.
If this is Wrong then tell me plz what should be output when N=-1

How about for N = 0?

Thank you very much sir.
My solution was not able to generate required result when N = 0
Now after the correction in my Solution my solution is accepted.
Again Thank you for help me.