while True:
    n = int(input())
    if n >=1 and n<=10**5:
        break

l = (input())
l = l.split(" ")
if len(l) == n:
    sm = 0
    flag=True
    for i in range (len(l)):
        if int(l[i])>=0 and int(l[i])<=10**18:
            sm += int(l[i])
        else:
            flag=False    
    if flag:
        if sm < 10:
            print (sm)
        else:
            while True:
                x = str(sm)
                sm = 0
                for i in range (len(x)):
                    sm += int(x[i])
                if sm < 10:
                    print (sm)
                    break