diff --git a/du5/program.c b/du5/program.c
index e95cdec..eab2ed7 100644
--- a/du5/program.c
+++ b/du5/program.c
@@ -14,12 +14,16 @@ typedef struct Tree {
 // читання дерева (preorder)
 Tree* readTree() {
     char line[SIZE];
+    int error = 0;
 
     if (fgets(line, SIZE, stdin) == NULL) return NULL;
 
     line[strcspn(line, "\r\n")] = 0;
 
-    if (line[0] == '\0') return NULL;
+    if (line[0] == '\0') {
+        error = 1;
+        return NULL;
+}
 
     Tree *node = (Tree*)malloc(sizeof(Tree));
     node->yes = NULL;
@@ -35,6 +39,10 @@ Tree* readTree() {
 
         node->yes = readTree();
         node->no = readTree();
+
+        if (!node->yes || !node->no) {
+            error = 1;
+        }
     }
 
     return node;
@@ -103,7 +111,7 @@ int main() {
 
     Tree *root = readTree();
 
-    if (!root) {
+    if (!root || error) {
         printf("Chybna databaza\n");
         return 0;
     }