Help me in solving PPSUM problem

help
,
1

My issue

Why did the testcase fail here?

My code

#include <stdio.h>

int main(void) {
	// your code goes here
	int t;
	scanf("%d",&t);
	while(t--){
	    int d,n,sum=0;
	    scanf("%d%d",&d,&n);
	    for(int i = 1;i<=(d*n);i++){
	        sum+=i;
	    }
	    printf("%d\n",sum);
	    
	}
	return 0;
}

Problem Link: PPSUM Problem - CodeChef

2

@vinodalaparthi
for test case
1
2 1
your output is 3
but the correct output will be 1