import math
N = int(input())
A = list(map(int, input().split()))

answer = A[0]
Sum = 0

def gcd(A,B):
    if(B == 0):
        return A
    else:
        return gcd(B, A%B)

#最小公倍数-1がfに入る数なはず
for i in range(1, N):
    answer = answer * A[i] // gcd(answer, A[i])
    
for i in range(N):
    Sum += (answer-1) % A[i]

print(Sum)