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