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";
}
}1487A - Arena | 1520D - Same Differences |
376A - Lever | 1305A - Kuroni and the Gifts |
1609A - Divide and Multiply | 149B - Martian Clock |
205A - Little Elephant and Rozdil | 1609B - William the Vigilant |
978B - File Name | 1426B - Symmetric Matrix |
732B - Cormen --- The Best Friend Of a Man | 1369A - FashionabLee |
1474B - Different Divisors | 1632B - Roof Construction |
388A - Fox and Box Accumulation | 451A - Game With Sticks |
768A - Oath of the Night's Watch | 156C - Cipher |
545D - Queue | 459B - Pashmak and Flowers |
1538A - Stone Game | 1454C - Sequence Transformation |
165B - Burning Midnight Oil | 17A - Noldbach problem |
1350A - Orac and Factors | 1373A - Donut Shops |
26A - Almost Prime | 1656E - Equal Tree Sums |
1656B - Subtract Operation | 1656A - Good Pairs |