Help me in solving SPREADCT problem

help
,
1

My issue

please give test cases for which my code is failing or logic to fix that corner test case which my code is unable to click

My code

#include <stdio.h>

long long sumOfPositiveIntegers(int x, int y) {
    return (y - x + 1) * (x + y) / 2;
}

void swap(long long *a, long long *b) {
    long long temp = *a;
    *a = *b;
    *b = temp;
}

int main()
{
	int T;
	scanf("%d",&T);
	while (T--)
	{
        long long N, M, K;
        long long ans=0, ans1=0;
        scanf("%lld%lld",&N,&M);
        if (N>M)
            swap(&N, &M);
        K= M/2;
            
        if (N > K+1)
        {
            ans= sumOfPositiveIntegers(N-K, K+1);
                ans*= (K+1);
            if (M%2 ==0)
            {
                ans1= sumOfPositiveIntegers(N-K, K+1);
                ans1*= K;
                ans+= ans1;
            }
        }
        else
        {
            ans= sumOfPositiveIntegers(1, N);
                ans*= (K+1);
            if (M%2 ==0)
            {
                ans1= sumOfPositiveIntegers(1, N);
                ans1*= K;
                ans+= ans1;
            }
        }
        ans= ans%998244353;
        printf("%lld\n",ans);
	}
	return 0;
}

Problem Link: Spread Spree Practice Coding Problem - CodeChef