diff --git a/du4/program.c b/du4/program.c
index c2352c0..b2017f5 100644
--- a/du4/program.c
+++ b/du4/program.c
@@ -6,10 +6,11 @@ int main(){
     int num1, num2, answer;
     char action;
     sscanf(read, "%d %c %d %*c %d", &num1, &action, &num2, &answer);
-    if(action != '/' || action != '*' || action != '-' ||action != '+'){
+    if(action != '/' && action != '*' && action != '-' && action != '+'){
         printf("CHYBA\n");
         return -1;
     }
     int check = (action == '/') ? num1 / num2 : (action == '*') ? num1 * num2 : (action == '+') ? num1 + num2 : num1 - num2;
     printf("%s\n", (check == answer) ? "OK" : "ZLE");
+
 }