N,M=map(int,input().split())
A=list(map(int,input().split()))

flag=[0 for i in range(M+1)]
for i in range(N):
    flag[A[i]]+=1
    
if M%2!=0:
    print(0)
    exit()

ans=0
for i in range(1,M//2+1):
    j=i+M//2
    ans+=flag[i]*flag[j]*(N-flag[i]-flag[j])
print(ans)