Calculate alternating sum of integers up to n

This C program calculates the alternating sum of integers from 1 to n, where n is provided by the user. It checks if n is within the range of 1 to 10^15 before performing the calculation. The result is printed as a long long integer.

#include<stdio.h>
#include<math.h>
int main()
{
    long long int n;
    long long int sum=0;
    scanf("%lld",&n);
    if(n>=1 && n<=pow(10,15)){
    for(int i=1;i<=n;i++)
    {
       long long int a=pow(-1,i)*i;
        //printf("%d\t%d\n",i,a);
        sum+=a;
    }
    printf("%lld\n",sum);}
    return 0;
}

Editor is loading...