// editor5
#include<iostream>
#include<string>
#include<cctype>
using namespace std;
int main(){
    string input;
    cin>>input;
    int start =0;
    if (intput [0]==' '){
        if(input.length()==1){
            cout<<"Invalid input";
            return 0;
            
        }
        start=1;
        
    }
    for(int i=start ;i<input.length();i++){
        if (!isdigit(input[i])){
            cout<,"invalid input";
            return 0;
        }
    }cout <<input.length()-start;
    return 0;
}