HTMLify

/** 
 * Forward declaration of guess API.
 * @param  num   your guess
 * @return 	     -1 if num is higher than the picked number
 *			      1 if num is lower than the picked number
 *               otherwise return 0
 * func guess(num int) int;
 */
func guessNumber(n int) int {
    l, u, gn := 1, n, n
    for ;; {
        g := guess(gn)
        if g == 0 {
            return gn
        }
        if g == +1 {
            l = gn
        }
        if g == -1 {
            u = gn
        }
        gn = (l+u)/2
    }
}