import sys
import math


def lcm(a, b):
    return a * b // math.gcd(a, b)


def input():
    return sys.stdin.readline().strip()


n = int(input())
a = list(map(int, input().split()))
a.sort()

a_lcm = a[0]
for ai in a:
    a_lcm = lcm(ai, a_lcm)

m = a_lcm - 1
ans = 0

for ai in a:
    ans += m%ai

print(ans)