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