diff --git a/tasks/calc/index.php b/tasks/calc/index.php
index e2382b1..e11b0aa 100644
--- a/tasks/calc/index.php
+++ b/tasks/calc/index.php
@@ -22,7 +22,7 @@
   $result = "";
 
   if (
-    array_key_exists("operand1", $_POST) &&
+    isset($_POST["operand1"], $_POST["operand2"], $_POST["operator"]) &&
     is_numeric($_POST["operand1"]) &&
     is_numeric($_POST["operand2"])
   ) {
@@ -55,7 +55,7 @@
   <form method="post" class="p-3 needs-validation" novalidate>
     <div class="mb-3">
       <label class="form-label" for="operand1">Operand 1</label>
-      <input class="form-control" id="operand1" type="number" name="operand1" value="0" required step="any" />
+      <input class="form-control" id="operand1" type="number" name="operand1" value="<?php echo is_numeric($result) ? $result : 0 ?>" required step="any" />
       <div class="invalid-feedback">
         Please enter a number
       </div>
@@ -66,7 +66,6 @@
       <div class="invalid-feedback">
         Please enter a number
       </div>
-
     </div>
 
     <label class="form-label">Operator</label>