import math
def lcm(x, y):
    return (x * y) // math.gcd(x, y)
n = int(input())
a = list(map(int,input().split()))
x = 1
for i in range(n-1):
    x *= lcm(a[i],a[i+1])
Sum = 0
for i in range(n):
    Sum += (x-1)%a[i]
print(Sum)