Bug in code of Longest Increasing Subsequence problem

[atinesh922]

Longest Increasing Subsequence

The Longest Increasing Subsequence problem is to find a subsequence of a given sequence in which the subsequence's elements are in sorted order and in which the subsequence is as long as possible.

I'm trying to implement a program for Longest Increasing Subsequence, It's giving correct output for some input patterns, But for some it's giving incorrect result. Can anybody tell me where is the bug in the code.
Here's my code

def binary_search(t, l, r, key):
    while (r - l > 1):
        m = l + (r - l)//2
        if (t[m]>=key):
            r = m
        else:
            l = m
    return r

def LIS():
    tailTable = [0] * N
    tailTable[0] = lst[0]
    len = 1
    for i in range(1, N):
        if (lst[i] < tailTable[0]):
            # New Smallest Value
            tailTable[0] = lst[i]
        elif (lst[i] > tailTable[len - 1]):
            # lst[i] wants to extend largest subsequence
            tailTable[len] = lst[i]
            len += 1
        else:
            # A[i] wants to be current end candidate of an existing
            # subsequence.
            tailTable[binary_search(tailTable, -1, len-1, lst[i])] = lst[i]
    
    return len
    
if __name__ == "__main__":
    N = int(input())
    
    lst = []
    for i in range(N):
        lst.append(input())
    ret = LIS()
    print(ret)