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: Wrong Answer)

T = gets.chomp
def count_pd str, pre_str
    return 0 if str.empty?
    c = str[0]
    cnt = 0
    if c == 'P'
        cnt += 1
    elsif cnt == 'D'
        cnt += 1
        cnt += 1 if pre_str == 'P'
    else
        cnt1, cnt2 = 0, 0
        cnt1 += count_pd(str[1..-1],'P')
        cnt2 += count_pd(str[1..-1],'D')
        cnt2 += 1
        cnt2 += 1 if pre_str == 'P'
        cnt = cnt1 > cnt2 ? cnt1 : cnt2
    end
    return cnt
end
ret = ''
T.size.times do |i|
    c = T[i]
    if c == '?'
        idx = T[i+1..-1].index('?') 
        if !idx
            ret << 'D'
            next
        else
            idx = idx + 1
        end
        trgt = T[i+1..i+idx]
        cnt1 = count_pd(trgt, 'P')
        cnt2 = count_pd(trgt, 'D')
        if cnt1 > cnt2
            ret << 'P'
        else
            ret << 'D'
        end
    else
        ret << c
    end
end
puts ret