diff --git a/du3/program.c b/du3/program.c
index b084532..740da66 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -2,7 +2,7 @@
 #include<assert.h>
 #include<string.h>
 #include<stdlib.h>
-
+#include<ctype.h>
 #define STACK_SIZE 10
 
 struct stack
@@ -81,6 +81,18 @@ void print_stack(struct stack* mystack)
     printf(" \n");
 }
 
+int is_whitespace_only(const char* str) 
+{
+    while (*str) 
+    {
+        if (!isspace((unsigned char)*str)) 
+	{
+            return 0;
+        }
+        str++;
+    }
+    return 1;
+}
 
 int main()
 {
@@ -91,6 +103,11 @@ int main()
         {	
             int flag=switch_operators(input);
             input[strcspn(input,"\n")]=0;
+	    if (strlen(input)==0 || is_whitespace_only(input))
+        	{
+                	printf("no input\n");
+            		return 0;
+        	}
             if (flag==0 || flag==-1)
             {
 			if(flag==-1 && mystack.values[mystack.size-1]==0)