diff --git a/cv3/program.c b/cv3/program.c
index f8060ef..3bad3d7 100644
--- a/cv3/program.c
+++ b/cv3/program.c
@@ -27,7 +27,7 @@ float getnpop(struct stack* stack)
 }
 
 
-float calculate(struct stack* stack, char operator)
+int calculate(struct stack* stack, char operator)
 {
     float num1 = getnpop(stack);
     float num2 = getnpop(stack);
@@ -45,11 +45,25 @@ float calculate(struct stack* stack, char operator)
             res = num1*num2;
         break;
         case '/':
+            if(num1 == 0)
+            {
+                //res = 1;
+                return 1;
+            }
             res = num2/num1;
         break;
     }
     add(stack, res);
-    return res;
+    return 0;
+}
+
+int check_op(char symb)
+{
+    if(symb == '+' || symb == '-' || symb == '*' || symb == '/')
+    {
+        return 1;
+    }
+    return 0;
 }
 
 int main(int argc, char const *argv[])
@@ -69,14 +83,18 @@ int main(int argc, char const *argv[])
         }
 
         buf[strcspn(buf, "\n")] = '\0';
-        num = atof(buf);
-        if(num != 0)
+        if(!check_op(buf[0]))
         {
+            num = atof(buf);
             add(&calc_stack, num);
         }
         else
         {
-            calculate(&calc_stack, buf[0]);
+            if(calculate(&calc_stack, buf[0]) == 1)
+            {
+                printf("division by zero\n");
+                return 0;
+            }
         }
         for (int i = 0; i < calc_stack.size; i++)
         {