diff --git a/du6/program.c b/du6/program.c
index ddcae3e..f144f8f 100644
--- a/du6/program.c
+++ b/du6/program.c
@@ -10,23 +10,15 @@ typedef struct tree {
     struct tree *right;
 } Tree;
 
-int valid_db = 1;
+int valid_db = 1;  // flag pre validitu databazy
 
-//odstranit koncovy znak
+// odstranit koncovy znak \n
 void strip_newline(char *s) {
     int len = strlen(s);
     if (len > 0 && s[len-1] == '\n')
         s[len-1] = '\0';
 }
 
-// uvolnenie pamate
-void destroy_tree(Tree *t) {
-    if (!t) return;
-    destroy_tree(t->left);
-    destroy_tree(t->right);
-    free(t);
-}
-
 // rekurzivne nacitanie stromu v preorder
 Tree* read_tree() {
     char buffer[SIZE];
@@ -34,7 +26,6 @@ Tree* read_tree() {
     if (!fgets(buffer, SIZE, stdin))
         return NULL;
 
-    // prazdny riadok -> koniec
     if (strcmp(buffer, "\n") == 0)
         return NULL;
 
@@ -45,35 +36,38 @@ Tree* read_tree() {
 
     strcpy(node->value, buffer);
 
-    // odpoved -> list
+    // list
     if (buffer[0] == '*') {
         return node;
     }
 
-    // inak nacitat oboch potomkov
+    // očakávame presne 2 potomkov
     node->left = read_tree();
-    node->right = read_tree();
-    
-    if (!node->left || !node->right) {
-    	valid_db = 0;
-	destroy_tree(node->left);
-	destroy_tree(node->right);
-	free(node);
-	return NULL;
+    if (!node->left) {
+        valid_db = 0;
+        free(node);
+        return NULL;
     }
 
-    long cur = ftell(stdin);
-    if (fgets(buffer, SIZE, stdin)) {
-    	if (strcmp(buffer, "\n") != 0 && buffer[0] != '*') {
-		valid_db = 0;
-	} else {
-		fseek(stdin, cur, SEEK_SET);
-	}
+    node->right = read_tree();
+    if (!node->right) {
+        valid_db = 0;
+        destroy_tree(node->left);
+        free(node);
+        return NULL;
     }
 
     return node;
 }
 
+// uvolnenie pamate
+void destroy_tree(Tree *t) {
+    if (!t) return;
+    destroy_tree(t->left);
+    destroy_tree(t->right);
+    free(t);
+}
+
 // pocet listov = pocet tovarov 
 int count_leaves(Tree *t) {
     if (!t) return 0;
@@ -90,19 +84,15 @@ void run_system(Tree *node) {
 
     // list -> koniec
     if (!node->left && !node->right) {
-	printf("Koniec\n");
+        printf("Koniec\n");
         return;
     }
 
-    int c;
-
-    do {
-	    c = getchar();
-	    if (c == EOF) {
-		    printf("Koniec vstupu\n");
-		    return;
-	    }
-    } while (c=='\n'  || c=='\r' || c==' ' || c=='\t');
+    char c;
+    if (scanf(" %c", &c) != 1) {
+        printf("Nerozumiem\n");
+        return;
+    }
 
     if (c == 'a') {
         run_system(node->left);
@@ -116,14 +106,14 @@ void run_system(Tree *node) {
 int main() {
     Tree *root = read_tree();
 
-    // nepodarilo sa nacitat koren -> chyba
+    // kontrola prázdneho alebo chybného stromu
     if (!root || !valid_db) {
         printf("Expert z bufetu to vie.\n");
-	printf("Chybna databaza\n");
+        printf("Chybna databaza\n");
         return 0;
     }
 
-    // skontrolovat prazdny riadok
+    // skontrolovat prazdny riadok po databaze
     char buffer[SIZE];
     if (!fgets(buffer, SIZE, stdin) || strcmp(buffer, "\n") != 0) {
         printf("Koniec vstupu\n");