diff --git a/du3/program.c b/du3/program.c
index b4c380c..e99c6e8 100644
--- a/du3/program.c
+++ b/du3/program.c
@@ -102,6 +102,11 @@ int main()
 				printf("division by zero\n");
 				return 0;
 			}
+			if(mystack.size==1)
+			{
+				printf("not enough operands\n");
+				return 0;
+			}
                 float op_num=pop_stack(&mystack,input);
                 push_stack(&mystack,op_num);
             }