N = int(input()) X = [int(x) for x in input().split(' ')] ans = 0 base = 1 for x in X: base *=x while sum(X)!=0: m = max(X) # 计算重复次数 rep = X.count(m) # 计算乘积 mul = 1 for x in X: mul *=x mul /= m**rep cnt = m**rep - (m-1)**rep ans += m*cnt*mul # 每一...