Try this;
<button type="button" formnovalidate>Cancel</button>
I changed your code: What you want is that your form should not be validated on click of cancel, so that's why i added the formnovalidate to the button cancel.
<form>
<input type="number" min="1" max="100" required />
<input type="submit">Add</input>
<input type="submit" formnovalidate>Cancel</input>
</form>