## Sum numbers from the visitor

importance: 5

Create a script that prompts the visitor to enter two numbers and then shows their sum.

Run the demoP.S. There is a gotcha with types.

```
let a = +prompt("The first number?", "");
let b = +prompt("The second number?", "");
alert( a + b );
```

Note the unary plus `+`

before `prompt`

. It immediately converts the value to a number.

Otherwise, `a`

and `b`

would be string their sum would be their concatenation, that is: `"1" + "2" = "12"`

.