Help me in solving COUNTP problem

help
,
1

My issue

What is mistake in my code

My code

# cook your dish here
for _ in range(int(input())):
    n=int(input())
    li=list(map(int,input().split()))
    a=[]
    b=[]
    # if n%2==0:
    li.sort()
    for i in range(len(li)):
        if i%2==0:
            a.append(li[i])
        else:
            b.append(li[i])
    
                
    a_s=sum(a)
    b_s=sum(b)
    if a_s*b_s%2!=0:
        print("YES")
    else:
        print("NO")

Problem Link: Counting Problem Practice Coding Problem - CodeChef