import sys
input=sys.stdin.readline
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    N=I()
    P=LI()
    
    def ch(x):
        temp=0
        while x!=0:
            temp+=x%10
            x=x//10
        return temp
    
    ans=0
    for i in range(N):
        P[i]=ch(P[i])
        ans+=P[i]
        
    while ans>=10:
        ans=ch(ans)
        
    print(ans)




main()