#include "gift.h"
#include<bits/stdc++.h>
using namespace std;
#define REP(i,n) for(int i = 0; i < n; i ++)
#define FOR(i,a,b) for(int i = a; i < b; i ++)
#define FORD(i,a,b) for(int i = a; i >= b; i --)
#define vi vector<int>
#define remin(a,b) a = min(a,b)
#define remax(a,b) a = max(a,b)
const int MX = 500005;
int lft[MX][3];
int dp[MX];
int pref[MX];
int breakable[MX];
int construct(int n, int r, vi a, vi b, vi x) {
REP(i,n+1){
lft[i][1] = i;
lft[i][2] = 0;
}
REP(i,r){
a[i]++;
b[i]++;
if(x[i] == 1){
remin(lft[b[i]][1],a[i]);
pref[a[i]]++;
pref[b[i]]--;
}
else remax(lft[b[i]][2],a[i]);
}
FOR(i,2,n+1) pref[i] += pref[i-1];
REP(i,n+1) breakable[i] = (pref[i] == 0);
FORD(i,n-1,1){
remin(lft[i][1],lft[i+1][1]);
}
FOR(i,2,n+1){
remax(lft[i][2],lft[i-1][2]);
}
dp[0] = 0;
int last = 0;
FOR(i,1,n+1){
dp[i] = -1;
if(last >= lft[i][2]){
dp[i] = last;
if(breakable[i]) last = i;
}
}
if(dp[n] == -1) return 0;
string s = "";
REP(i,n) s += 'R';
int cur = 0;
int ind = n;
while(ind){
if(cur){
FOR(i,dp[ind],ind) s[i] = 'B';
}
cur = 1-cur;
ind = dp[ind];
}
craft(s);
return 1;
}
