diff --git a/a4/a4.c b/a4/a4.c
deleted file mode 100644
index 354499a..0000000
--- a/a4/a4.c
+++ /dev/null
@@ -1 +0,0 @@
-#include<stdio.h>
diff --git a/du4/Makefile b/du4/Makefile
new file mode 100644
index 0000000..07ca630
--- /dev/null
+++ b/du4/Makefile
@@ -0,0 +1,13 @@
+CC = gcc
+CFLAGS = -std=c11 -Wall -Wextra -Werror
+
+TARGET = game
+SRC = game.c
+
+all: $(TARGET)
+
+$(TARGET): $(SRC)
+	$(CC) $(CFLAGS) $(SRC) -o $(TARGET)
+
+clean:
+	rm -f $(TARGET)
diff --git a/du4/game.c b/du4/game.c
new file mode 100644
index 0000000..4e68f30
--- /dev/null
+++ b/du4/game.c
@@ -0,0 +1,160 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "a4.h"
+
+int error = 0;
+
+typedef struct Tree {
+    char text[SIZE];
+    int isAnswer;
+    struct Tree *yes;
+    struct Tree *no;
+} Tree;
+
+// uvolnenie pamate
+void freeTree(Tree *node) {
+    if (!node) return;
+
+    freeTree(node->yes);
+    freeTree(node->no);
+    free(node);
+}
+
+// citanie stromu (preorder)
+Tree* readTree() {
+    char line[SIZE];
+
+    if (fgets(line, SIZE, stdin) == NULL) {
+        error = 1;
+        return NULL;
+    }
+
+    // odstranenie konca riadku
+    line[strcspn(line, "\r\n")] = '\0';
+
+    // prazdny riadok = chyba
+    if (line[0] == '\0') {
+        error = 1;
+        return NULL;
+    }
+
+    Tree *node = (Tree*)malloc(sizeof(Tree));
+
+    if (!node) {
+        error = 1;
+        return NULL;
+    }
+
+    node->yes = NULL;
+    node->no = NULL;
+
+    // list
+    if (line[0] == '*') {
+        node->isAnswer = 1;
+        strcpy(node->text, line + 1);
+    }
+    // otazka
+    else {
+        node->isAnswer = 0;
+        strcpy(node->text, line);
+
+        node->yes = readTree();
+        node->no = readTree();
+
+        if (!node->yes || !node->no) {
+            error = 1;
+            freeTree(node);
+            return NULL;
+        }
+    }
+
+    return node;
+}
+
+// kontrola prazdneho riadku po strome
+int EmptyLine() {
+    char line[SIZE];
+
+    if (fgets(line, SIZE, stdin) == NULL)
+        return 1;
+
+    return strcmp(line, "\n") == 0 ||
+           strcmp(line, "\r\n") == 0;
+}
+
+// pocet listov
+int Leaves(Tree *node) {
+    if (!node) return 0;
+
+    if (node->isAnswer)
+        return 1;
+
+    return Leaves(node->yes) + Leaves(node->no);
+}
+
+// hra
+void start(Tree *node) {
+    char input[SIZE];
+
+    while (node && !node->isAnswer) {
+
+        printf("%s\n", node->text);
+
+        if (fgets(input, SIZE, stdin) == NULL) {
+            printf("Koniec vstupu\n");
+            return;
+        }
+
+        int i = 0;
+
+        while (input[i] == ' ' || input[i] == '\t')
+            i++;
+
+        if (input[i] == 'a' || input[i] == 'A') {
+            node = node->yes;
+        }
+        else if (input[i] == 'n' || input[i] == 'N') {
+            node = node->no;
+        }
+        else {
+            printf("Nerozumiem\n");
+            return;
+        }
+    }
+
+    if (node && node->isAnswer) {
+        printf("%s\n", node->text);
+        printf("Koniec\n");
+    }
+}
+
+int main() {
+
+    printf("Expert z bufetu to vie.\n");
+
+    Tree *root = readTree();
+
+    if (!root || error) {
+        printf("Chybna databaza\n");
+        freeTree(root);
+        return 0;
+    }
+
+    // po strome musi byt prazdny riadok
+    if (!EmptyLine()) {
+        printf("Chybna databaza\n");
+        freeTree(root);
+        return 0;
+    }
+
+    printf("Pozna %d druhov ovocia a zeleniny.\n", Leaves(root));
+    printf("Odpovedajte 'a' pre prvu moznost alebo 'n' pre druhu moznost.\n");
+
+    start(root);
+
+    freeTree(root);
+
+    return 0;
+}
+
diff --git a/a4/a4.h b/du4/game.h
similarity index 67%
rename from a4/a4.h
rename to du4/game.h
index dac4495..3a0cb56 100644
--- a/a4/a4.h
+++ b/du4/game.h
@@ -1,5 +1,5 @@
-#ifndef A4_H
-#define A4_H
+#ifndef GAME_H
+#define GAME_H
 
 #define SIZE 256
 
@@ -10,19 +10,10 @@ typedef struct Tree {
     struct Tree *no;
 } Tree;
 
-// citanie stromu
 Tree* readTree();
-
-// kontrola prazdneho riadku
 int EmptyLine();
-
-// pocet listov
 int Leaves(Tree *node);
-
-// uvolnenie pamate
 void freeTree(Tree *node);
-
-// hra
 void start(Tree *node);
 
 #endif