#include<iostream>#include<algorithm>#include<cmath>#include<cstring>#include<vector>#include<unordered_map>#include<unordered_set>#include<set>#include<map>#defineendl'\n'#defineIOSios::sync_with_stdio(false); cin.tie(0); cout.tie(0)usingnamespace std;constdouble pi =acos(-1);typedeflonglong ll;voidsolve(){int n;string s;cin >> n >> s;int p1 =-1;for(int i =0; i < s.size(); i ++)if(s[i]!='?'){p1 = i;break;}if(p1 ==-1){char c ='B';for(int i =0; i < s.size(); i ++){cout << c;if(c =='B') c ='R';else c ='B';}cout << endl;return;}for(int i = p1; i >=0; i --){if(s[i]=='?'){if(s[i +1]=='B') s[i]='R';else s[i]='B';}}for(int i = p1; i < s.size(); i ++){if(s[i]=='?'){if(s[i -1]=='B') s[i]='R';else s[i]='B';}}cout << s << endl;}intmain(){IOS;int T;cin >> T;while(T --){solve();}return0;}