let s1 = "str1";
let s2 = "str2";

let s3 = s1 + " - " + s2;
s3;
len(s3); 


let x = 10;
let y = 20;

let sum = fn(a, b){ a + b;};
sum(x, y);

let arr = [1, 2, 3, 4];
sum(arr[0], arr[3]);

let dict = {"one": 1, "two": 2, "three": 3};
sum(dict["one"], dict["two"]);

let fact = fn(x){ if (x > 1) { x * fact(x - 1);} else {1}};
fact(10);

exit