diff --git a/du4/program.c b/du4/program.c
index 023fb16..1b7baea 100644
--- a/du4/program.c
+++ b/du4/program.c
@@ -4,7 +4,7 @@
 #include <ctype.h>
 
 int call(float A, float B, float C, char AC){
-    if(AC=='/'&&B==0){
+    if(AC=='/'&&B==0||AC!=('+'||'-'||'*'||'-')){
         return printf("CHYBA\n");;
     }
     else if(AC=='+'){