class Scanner {
    private var stack = [String]()
    private var index = 0
    
    func peek() -> String {
        if stack.count == index {
            stack += readLine()!.split(separator: " ").map{ String($0) }
        }
        return stack[index]
    }
    
    func next() -> String {
        let value = peek()
        index += 1
        return value
    }
    
    func nextInt() -> Int {
        return Int(next())!
    }
    
    func nextDouble() -> Double {
        return Double(next())!
    }
}

extension String {
    var characters: [Character] {
        self.map{ $0 }
    }
}

var scanner = Scanner()
let s = scanner.next()
print(s.filter { $0 != "0" }.count - 1)