n=int(input())
s=input()
if len(set(el for el in s))==1:
print(s[0])
elif n==1:
print(s)
elif n==2:
if "R" not in s:
print("R")
elif "G" not in s:
print("G")
else :
print("B")
else :
a=s.count("R")
b=s.count("G")
c=s.count("B")
p=sum(int(el>=2 ) for el in [a,b,c])
if a and b and c:
print('BGR')
elif p>=2:
print("BGR")
else :
if a>1:
if b or c:
print("BG")
else :
print("R")
elif b>1:
if a or c :
print("BR")
else :
print("G")
else :
if a or b:
print("GR")
else:
print("B")#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007
int main() {
int a;cin>>a;
string s;cin>>s;
int g=0,b=0,r=0;
for(int i=0;i<s.length();i++){
if(s[i]=='R')r++;
if(s[i]=='G')g++;
if(s[i]=='B')b++;
}
if(r>0&&b>0&&g>0)cout<<"BGR";
else if((r==0&&b>1&&g>1)||(b==0&&r>1&&g>1)||(g==0&&b>1&&r>1))cout<<"BGR";
else if(r==0&&b==g&&g==1)cout<<"R";
else if(b==0&&g==r&&r==1)cout<<"B";
else if(g==0&&b==r&&r==1)cout<<"G";
else if(b&&r+g==0)cout<<"B";
else if(r&&b+g==0)cout<<"R";
else if(g&&r+b==0)cout<<"G";
else if(g>1&&b+r==1){
cout<<"BR";
}
else if(b>1&&g+r==1){
cout<<"GR";
}
else {
cout<<"BG";
}
}1511C - Yet Another Card Deck | 1698A - XOR Mixup |
1702E - Split Into Two Sets | 1703B - ICPC Balloons |
1702F - Equate Multisets | 1700A - Optimal Path |
665C - Simple Strings | 1708A - Difference Operations |
1703E - Mirror Grid | 1042A - Benches |
1676B - Equal Candies | 1705B - Mark the Dust Sweeper |
1711A - Perfect Permutation | 1701B - Permutation |
1692A - Marathon | 1066A - Vova and Train |
169B - Replacing Digits | 171D - Broken checker |
380C - Sereja and Brackets | 1281B - Azamon Web Services |
1702A - Round Down the Price | 1681C - Double Sort |
12A - Super Agent | 1709A - Three Doors |
1680C - Binary String | 1684B - Z mod X = C |
1003A - Polycarp's Pockets | 1691B - Shoe Shuffling |
1706A - Another String Minimization Problem | 1695B - Circle Game |