#include<iostream>
using namespace std;
int main(){
    string s,c="";
    getline(cin,s);
    for(int i=0;i<s.lenght();i++)
    {
        if(s[i]=="-"){
            cout<<"Invalid input";
        }
        if(s[i]>='A'&&s[i]<='Z')||(s[i]>='a'&& s[i]<='z')||(s[i]>='0'&&s[i]<='9')){
            c+=s[i];
        }
    }
    cout<<c;
    return 0;
}