Problem:
Score : 200 points

Problem Statement

For a string S consisting of the uppercase English letters P and D, let the doctoral and postdoctoral quotient of S be the total number of occurrences of D and PD in S as contiguous substrings. For example, if S = PPDDP, it contains two occurrences of D and one occurrence of PD as contiguous substrings, so the doctoral and postdoctoral quotient of S is 3.

We have a string T consisting of P, D, and ?.

Among the strings that can be obtained by replacing each ? in T with P or D, find one with the maximum possible doctoral and postdoctoral quotient.

Constraints

1 \leq |T| \leq 2 \times 10^5

T consists of P, D, and ?.

Input

Input is given from Standard Input in the following format:

T

Output

Print one string with the maximum possible doctoral and postdoctoral quotient among the strings that can be obtained by replacing each ? in T with P or D.
If there are multiple such strings, you may print any of them.

Sample Input 1

PD?D??P

Sample Output 1

PDPDPDP

This string contains three occurrences of D and three occurrences of PD as contiguous substrings, so its doctoral and postdoctoral quotient is 6, which is the maximum doctoral and postdoctoral quotient of a string obtained by replacing each ? in T with P or D.

Sample Input 2

P?P?

Sample Output 2

PDPD

Solution in Ruby (2.7.1) (judge verdict: Time Limit Exceeded)

T = gets.chomp
@ret = []
def count_pd str, pre_char='' 
    cnt = 0
    if str[0] == 'P'
        cnt += count_pd(str[1..-1], str[0])
    elsif str[0] == 'D'
        cnt += 1 
        cnt += 1 if pre_char == 'P'
        cnt += count_pd(str[1..-1], str[0])
    elsif str[0] == '?'
        cnt1 = count_pd(str[1..-1], 'P')
        cnt2 = count_pd(str[1..-1], 'D')
        if pre_char == 'P'
            cnt2 += 2
        else
            cnt2 += 1
        end
        if cnt1 >= cnt2
            @ret << 'P'
            cnt += cnt1
        else
            @ret << 'D'
            cnt += cnt2
        end
    end
    return cnt
end
cnt = count_pd(T)
ret = ''
T.chars.each do |c|
    if c == '?'
        ret << @ret.pop
    else
        ret << c
    end
end
puts ret