# Dynamic Programming implementation of LCS problem 

def lcs(X , Y): 
    # find the length of the strings 
    m = len(X) 
    n = len(Y) 
  
    # declaring the array for storing the dp values 
    L = [[None]*(n+1) for i in xrange(m+1)] 
  
    for i in range(m+1): 
        for j in range(n+1): 
            if i == 0 or j == 0 : 
                L[i][j] = 0
            elif X[i-1] == Y[j-1]: 
                L[i][j] = L[i-1][j-1]+1
            else: 
                L[i][j] = max(L[i-1][j] , L[i][j-1]) 
  
    # L[m][n] contains the length of LCS of X[0..n-1] & Y[0..m-1] 
    return L[m][n] 
#end of function lcs 
  
  
# Driver program to test the above function 
X = "AGGTAB"
Y = "GXTXAYB"
print "Length of LCS is ", lcs(X, Y)