[рони]

(1<=num<=100).

function fn(b, d) {
    function e() {
        var a = b + Math.random() * (d + 1 - b) | 0,
            c = prompt("Ваше число " + a + "?", "smaller/bigger/yes");
        "yes" == c ? alert(a + "!!!") : ("bigger" == c && (b = a), "smaller" == c && (d = a), e())
    }
    e()
};
fn(1,100)