#include<iostream>
#include<string>
using namespace std;
int main()
{
    string input;
    cin>>input;
    if (input.empty()){
        cout<<"Invalid input";
        return 0;
    }
    int start =0;
    if(input[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<<inp.length()-start;
    return 0;
}