def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))
mod=10**9+7

def main():
    C=input()
    
    ans=0
    for i in range(len(C)-1):
        if C[i+1]!="0":
            ans+=1
            
    print(ans)


main()