#include <iostream>
#include <string> 
#include <cctype>
using namespace std;
int main(){
    string str;
    getline(cin,str);
    if(str.length()==0){
        cout<<"Invalid input";
        return 0;
    }
    string result="";
    for (char ch:str){
        if(!(isalpha(ch)||ch =' ')){
            cout<<"Invalid input";
            return 0;
        }
        if (ch!=' '){
            result +=ch;
        }
    }
    cout<<result;
}