#include<iostream>
#include<string>
using namespace std;

int main() {
    stirng s;
    cin >>s;
    
    int start = 0;
    
    if (s[0]== '-') {
        if (s.length() == 1) {
            cout << "Invalid input";
            return 0;
        }
        start = 1;
    }
    for (int i = start; i < s.length(); i++) {
        if (!isdigit(s[i])) {
            cout << "Invalid input";
            return 0;
        }
    }
    cout << s.length() - start;
    return 0;
}