// editor5
#include<iostream>
#include<string>
using namespace std;
int main() {
    string s;
    if(!(cin>>s)) return 0;
    int a=0;
    for(char c :s){
        if(isdigit(c))a++;
        else if (!(isdigit(c)){
            return 0;
        }
    }
    if(a == 0) <<"Invalid input";
    else cout<<a;
}