#include <iostream>
#include <cstring>
using namespace std;
int main()
{
    char s[31],*p;
    cin.get(s,30);
    p=strtok(s," ");
    while(p!=NULL){
        if(strlen(p)==2)
            cout<<p<<'\n';
        p=strtok(NULL," ");
    }
    return 0;
}