import random

def calc(A):
    n = len(A)
    res = 0
    for i in range(0,n):
        for j in range(i+1, n):
            res += A[j] - A[i]
    return res

def calc2(A):
    n = len(A)
    res = 0
    for i in range(0,n):
        res += (2*(i+1)-n-1)*A[i]
    return res

def main():
    for i in range(0,100):
        A = []
        for j in range(0,i):
            A.append(random.randint(0,1000000))
        if not calc(A) == calc2(A):
            print("wrong!")
            return
    print("ok!")

if __name__ == "__main__":
    main()