from math import floor
def bsa(a, n, t):
    lft = 0
    rgt = n -1
    while lft <= rgt:
        m = floor((lft + rgt) / 2)
        if a[m] < t:
            lft = m+1
        elif a[m] > t:
            rgt = m-1
        else:
            return m
    return -1