#include<iostream.
#include<string>
using namespace std;
int main(){
    string input;
    cin>>input;
    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<<input.length() - start;
    return 0;
}