l = input()
m = list(l)

nums = []

for i in range(len(m)):
    i = int(i)
    try:
        n = int(m[i])
        nums.append(n)
    except ValueError:
        pass

total = 0

for i in range(len(nums)):
    i = int(i)
    total += int(nums[i])

print(total)