C.cpp

#include <bits/stdc++.h>
#define vi vector<int>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define F first
#define S second
#define mp map<int, int>
#define ump unordered_map<int, int>
#define ll long long int
#define pb push_back
#define mod 1000000007
#define int long long
#define pr1             \
    cout << -1 << endl; \
    return;
#define all(v) v.begin(), v.end()
#define loop(i, x, n) for (int i = x; i < n; i++)
#define rloop(i, n) for (int i = n - 1; i >= 0; i--)
#define test  \
    int t;    \
    cin >> t; \
    while (t--)
using namespace std;
/*************************************************************************************************/
void solve()
{
    int n;
    string s;
    set<int> r, d;
    cin >> n >> s;
    loop(i, 0, n)
    {
        if (s[i] == 'D')
            d.insert(i);
        else
            r.insert(i);
    }
    while (true)
    {
        loop(i, 0, n)
        {
            if (d.size() == 0)
            {
                cout << 'R';
                return;
            }
            if (r.size() == 0)
            {
                cout << 'D';
                return;
            }
            if (s[i] == 'D' and d.count(i))
            {
                auto it = r.lower_bound(i);
                if (it == r.end())
                    r.erase(r.begin());
                else
                    r.erase(it);
            }
            if (s[i] == 'R' and r.count(i))
            {
                auto it = d.lower_bound(i);
                if (it == d.end())
                    d.erase(d.begin());
                else
                    d.erase(it);
            }
        }
    }
}
signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    //test
    solve();
    return 0;
}