сумма цифр

sum = 0
def popa1(a,b):
    if a//b > 0:
        return popa1(a,b*10)
    else:
        return b
def popa2(a,b):
    global sum
    sum += a//b
    a= a - ((a//b)*b)
    b = b // 10
    if b < 1:
        return sum
    else:
        return popa2(a,b)
a = int(input())
f = popa1(a,1 )
print(popa2(a,f))