#include<iostream>
#include<string>
using namespace std;
int main(){
    string text;
    getline(cin,text);
    if(text.length()==0){
        cout<<"Invalid input";
        return 0;
    }
    for(char ch:text)
    {
        if(isdigit(ch))
        {
            cout<<"Invalid input";
            return 0;
        }
    }
    string result ="";
    for(char ch::t)
}