To store continuous backward occurence
for i in range ( N - 1 , - 1 , - 1 ) : NEW_LINE INDENT if i == N - 1 or A [ i ] != A [ i + 1 ] : NEW_LINE INDENT backward [ i ] = 1 NEW_LINE DEDENT else : NEW_LINE INDENT backward [ i ] = backward [ i + 1 ] + 1 NEW_LINE DEDENT DEDENT