diff --git a/du6/program.c b/du6/program.c
new file mode 100644
index 0000000..79de6aa
--- /dev/null
+++ b/du6/program.c
@@ -0,0 +1,120 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#define SIZE 256
+
+struct tree 
+{
+    char value[SIZE];
+    struct tree* left;
+    struct tree* right;
+};
+
+struct tree* read_tree() 
+{
+    char buffer[SIZE];
+    if (fgets(buffer, SIZE, stdin)==NULL) 
+    {
+        return NULL;
+    }
+    if (buffer[0]=='\n') 
+    {
+        return NULL;
+    }
+    struct tree* node=(struct tree*)calloc(1, sizeof(struct tree));
+    strcpy(node->value, buffer);
+    if (buffer[0]!='*') 
+    {
+        node->left=read_tree();
+        node->right=read_tree();
+    }
+    return node;
+}
+
+void destroy_tree(struct tree* tree) 
+{
+    if (tree==NULL) 
+    {
+        return;
+    }
+    destroy_tree(tree->left);
+    destroy_tree(tree->right);
+    free(tree);
+}
+
+int count_answers(struct tree* tree) 
+{
+    if (tree==NULL) 
+    {
+        return 0;
+    }
+    if (tree->value[0]=='*') 
+    {
+        return 1;
+    }
+    return count_answers(tree->left)+count_answers(tree->right);
+}
+
+void run_knowledge_system(struct tree* node) 
+{
+    if (node==NULL) 
+    {
+        return;
+    }
+    printf("%s", node->value);
+    if (node->value[0]=='*') 
+    {
+        return;
+    }
+    if (node->left!=NULL || node->right!=NULL) 
+    {
+        char answer[10];
+        if (fgets(answer, sizeof(answer), stdin)==NULL) 
+        {
+            printf("Koniec\n");
+            return;
+        }
+        if (answer[0]=='a') 
+        {
+            run_knowledge_system(node->left);
+        } 
+        else if (answer[0]=='n') 
+        {
+            run_knowledge_system(node->right);
+        }
+        else 
+        {
+            printf("Nespravny vstup.\n");
+            return;
+        }
+    }
+}
+
+int main() 
+{
+    struct tree* knowledge_base=read_tree();
+    char empty_line[SIZE];
+    if (fgets(empty_line, SIZE, stdin)==NULL || empty_line[0]!='\n') 
+    {
+        printf("Nespravna baza pravidiel.\n");
+        if (knowledge_base!=NULL) 
+        {
+            destroy_tree(knowledge_base);
+        }
+        return 1;
+    }
+    if (knowledge_base==NULL) 
+    {
+        printf("Nespravna baza pravidiel.\n");
+        return 1;
+    }
+    int answer_count=count_answers(knowledge_base);
+    printf("MUDrC to vie.\n");
+    printf("Pozna %d druhov ovocia a zeleniny.\n",answer_count);
+    printf("Odpovedajte 'a' alebo 'n'\n");
+    run_knowledge_system(knowledge_base);
+    destroy_tree(knowledge_base);
+    return 0;
+}