import sys
nums = list(map(int, sys.stdin.read().split()))
data = []
numbers = []
result = 0
for el in nums:
data.append(el)
number_input = data[0]
while (number_input > 0):
last_num = number_input % 10
result += last_num
numbers.append(last_num)
number_input //= 10
print(result)
aW1wb3J0IHN5cwoKbnVtcyA9IGxpc3QobWFwKGludCwgc3lzLnN0ZGluLnJlYWQoKS5zcGxpdCgpKSkKZGF0YSA9IFtdCm51bWJlcnMgPSBbXQpyZXN1bHQgPSAwCgpmb3IgZWwgaW4gbnVtczoKCWRhdGEuYXBwZW5kKGVsKQoJCm51bWJlcl9pbnB1dCA9IGRhdGFbMF0KCndoaWxlIChudW1iZXJfaW5wdXQgPiAwKToKCWxhc3RfbnVtID0gbnVtYmVyX2lucHV0ICUgMTAKCXJlc3VsdCArPSBsYXN0X251bQoJbnVtYmVycy5hcHBlbmQobGFzdF9udW0pCgludW1iZXJfaW5wdXQgLy89IDEwCgpwcmludChyZXN1bHQp