#include<iostream>
#include<string>
using namespace std;
int main()
{
    stringinput;
    getline(cin, input);
    if(input.find('-') !-string::npos)
    {
        cout<<"Invalid input";
    }
    else
    {
        string cleaned
        for(char c: input)
        {
            if(isalnum(c))
            {
                cleaned +=c;
            }
        }
        cout<<cleaned;
    }
    return 0;
}