#include <iostream>

#include <sstream>

#include <algorithm>

#include <cstdio>

#include <math.h>

#include <set>

#include <map>

#include <queue>

#include <string>

#include <string.h>

#include <bitset>

#define REP(i,a,n) for(int i=a;i<=n;++i)

#define PER(i,a,n) for(int i=n;i>=a;--i)

#define hr putchar(10)

#define pb push_back

#define lc (o<<1)

#define rc (lc|1)

#define mid ((l+r)>>1)

#define ls lc,l,mid

#define rs rc,mid+1,r

#define x first

#define y second

#define io std::ios::sync_with_stdio(false)

#define endl '\n'

#define DB(a) ({REP(__i,1,n) cout<<a[__i]<<' ';hr;})

using namespace std;

typedef long long ll;

typedef pair<int,int> pii;

const int P = 1e9+7, INF = 0x3f3f3f3f;

ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;}

ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;}

ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;}

inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;}

//head

const int N = 1e6+10;

int n, a[N];

char s[N], b[2][2]{"R","D"};

set<int> q, g[2];

int main() {

	scanf("%d%s", &n, s);

	REP(i,0,n-1) {

		a[i]=s[i]=='D';

		q.insert(i);

		g[a[i]].insert(i);

	}

	REP(i,0,1) if (g[!i].empty()) return puts(b[i]),0;

	while (q.size()) {

		int x = *q.begin(); q.erase(x);

		int id = a[x%n], now = x/n;

		auto t = g[!id].lower_bound(x%n);

		if (t==g[!id].end()) t=g[!id].begin(),++now;

		q.erase(now*n+*t);

		g[!id].erase(t);

		if (g[!id].empty()) return puts(b[id]),0;

		q.insert(x+n);

	}

}