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