import math

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

n=int(input())
a=list(map(int,input().split()))
for i in range(n-1):    
    if(i==0):
        m=lcm(a[0],a[1])
    else:
        m=lcm(m,a[i+1])
m-=1
f=0
for i in range(n):
    f+=m%a[i]
print(f)