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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Linq;
using CompLib.Util;

public class Program
{

    public void Solve()
    {
        var sc = new Scanner();
        string t = sc.Next();
        int n = t.Length;

        // iまで見た 最後が 0 P 1 Dのときの最大
        int[,] dp = new int[n, 2];
        for (int i = 0; i < n; i++)
        {
            dp[i, 0] = int.MinValue;
            dp[i, 1] = int.MinValue;
        }
        if (t[0] == 'P' || t[0] == '?')
        {
            dp[0, 0] = 0;
        }
        if (t[0] == 'D' || t[0] == '?')
        {
            dp[0, 1] = 1;
        }

        for (int i = 1; i < n; i++)
        {
            if (t[i] == 'P' || t[i] == '?')
            {
                dp[i, 0] = Math.Max(dp[i - 1, 0], dp[i - 1, 1]);
            }
            if (t[i] == 'D' || t[i] == '?')
            {
                dp[i, 1] = Math.Max(dp[i - 1, 0] + 2, dp[i - 1, 1] + 1);
            }
        }

        var ans = new char[n];
        int last;
        if (dp[n - 1, 0] < dp[n - 1, 1])
        {
            ans[n - 1] = 'D';
            last = 1;
        }
        else
        {
            ans[n - 1] = 'P';
            last = 0;
        }
        for (int i = n - 2; i >= 0; i--)
        {
            // p
            if ((last == 0 && dp[i, 0] == dp[i + 1, 0]) || (last == 1 && dp[i, 0] + 2 == dp[i + 1, 1]))
            {
                ans[i] = 'P';
                last = 0;
            }
            else
            {
                ans[i] = 'D';
                last = 1;
            }
        }

        Console.WriteLine(new string(ans));
    }

    public static void Main(string[] args) => new Program().Solve();
}

namespace CompLib.Util
{
    using System;
    using System.Linq;

    class Scanner
    {
        private string[] _line;
        private int _index;
        private const char Separator = ' ';

        public Scanner()
        {
            _line = new string[0];
            _index = 0;
        }

        public string Next()
        {
            while (_index >= _line.Length)
            {
                _line = Console.ReadLine().Split(Separator);
                _index = 0;
            }

            return _line[_index++];
        }

        public int NextInt() => int.Parse(Next());
        public long NextLong() => long.Parse(Next());
        public double NextDouble() => double.Parse(Next());
        public decimal NextDecimal() => decimal.Parse(Next());
        public char NextChar() => Next()[0];
        public char[] NextCharArray() => Next().ToCharArray();

        public string[] Array()
        {
            _line = Console.ReadLine().Split(Separator);
            _index = _line.Length;
            return _line;
        }

        public int[] IntArray() => Array().Select(int.Parse).ToArray();
        public long[] LongArray() => Array().Select(long.Parse).ToArray();
        public double[] DoubleArray() => Array().Select(double.Parse).ToArray();
        public decimal[] DecimalArray() => Array().Select(decimal.Parse).ToArray();
    }
}