from functools import reduce


def gcd(a, b):
    while b:
        a, b = b, a % b
    return a


def lcm_base(x, y):
    return (x * y) // gcd(x, y)


def lcm(numbers):
    return reduce(lcm_base, numbers, 1)


N = int(input())
a = list(map(int, input().split()))

mod = []
for m in range(lcm(a)):
    k = [m % a[i] for i in range(N)]
    mod.append(sum(k))
print(max(mod))
