Count the frequency of each digit
for i in range ( number_of_digits ) : NEW_LINE INDENT if ( s [ i ] == '1' or s [ i ] == '2' or s [ i ] == '3' or s [ i ] == '5' or s [ i ] == '7' ) : NEW_LINE INDENT freq [ ord ( s [ i ] ) - 48 ] += 1 ; NEW_LINE DEDENT DEDENT