def solve(a):
    n1 = a.count(1) # no. of 1's in a
    n2 = a.count(2) # no. of 2's in a
    n = len(a)
    
    cnt_1_1 = n1*(n1 - 1)//2  # no. of (1,1) pairs
    cnt_2_2 = n2*(n2 - 1)//2  # no. of (2,2) pairs
    cnt_1_n = n1*(n - n1)    #  no. of (1,n) pairs
    
    return 2*cnt_1_1 + cnt_2_2 + cnt_1_n