import math
from functools import reduce

def lcm_base(x, y):
    return (x * y)//math.gcd(x, y)
def lcm(*numbers):
    return reduce(lcm_base, numbers, 1)

N = int(input())
a = list(map(int, input().split()))
lcm = lcm(*a)-1
f = 0
for i in range(len(a)):
    f += lcm%a[i]
print(f)