#include <stdio.h>
#include <string.h>

char back[100][50];
char forward[100][50];
char current[50] = "";

int b,f = -1;

void visit(char *url){
    strcpy(back[++b], current);
    strcpy(current, url);
}

void goBack(){
    strcpy(forward[++f], current);
    strcpy(current, back[b--]);
}

void goForward(){
    strcpy(back[++b], current);
    strcpy(current, forward[f--]);
}

int main(){
    visit("google.com");
    visit("naver.com");
    visit("youtube.com");

    goBack();
    goBack();
    goForward();

    printf("%s\n", current);
}