// #pragma GCC target("avx")  // CPU 処理並列化
// #pragma GCC optimize("O3")  // CPU 処理並列化
// #pragma GCC optimize("unroll-loops")  // 条件処理の呼び出しを減らす
// #define BEGIN_STACK_EXTEND(size) void * stack_extend_memory_ = malloc(size);void * stack_extend_origin_memory_;char * stack_extend_dummy_memory_ = (char*)alloca((1+(int)(((long long)stack_extend_memory_)&127))*16);*stack_extend_dummy_memory_ = 0;asm volatile("mov %%rsp, %%rbx\nmov %%rax, %%rsp":"=b"(stack_extend_origin_memory_):"a"((char*)stack_extend_memory_+(size)-1024));
// #define END_STACK_EXTEND asm volatile("mov %%rax, %%rsp"::"a"(stack_extend_origin_memory_));free(stack_extend_memory_);

#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<queue>
#include<deque>
#include<stack>
#include<string>
#include<string.h>
#include<vector>
#include<set>
#include<map>
#include<bitset>
#include<stdlib.h>
#include<cassert>
#include<time.h>
#include<bitset>
#include<numeric>
#include<unordered_set>
#include<unordered_map>
#include<complex>
using namespace std;
const long long mod=998244353;
const long long inf=mod*mod;
const long long d2=(mod+1)/2;
const long double EPS=1e-9;
const long double INF=1e+10;
const long double PI=acos(-1.0);
const int C_SIZE = 3100000;
const int UF_SIZE = 3100000;
namespace{
	long long fact[C_SIZE];
	long long finv[C_SIZE];
	long long inv[C_SIZE];
	long long Comb(int a,int b){
	 	if(a<b||b<0)return 0;
	 	return fact[a]*finv[b]%mod*finv[a-b]%mod;
	}
	void init_C(int n){
		fact[0]=finv[0]=inv[1]=1;
		for(int i=2;i<n;i++){
			inv[i]=(mod-(mod/i)*inv[mod%i]%mod)%mod;
		}
		for(int i=1;i<n;i++){
			fact[i]=fact[i-1]*i%mod;
			finv[i]=finv[i-1]*inv[i]%mod;
		}
	}
	long long pw(long long a,long long b){
		if(a<0LL)return 0;
		if(b<0LL)return 0;
		long long ret=1;
		while(b){
			if(b%2)ret=ret*a%mod;
			a=a*a%mod;
			b/=2;
		}
		return ret;
	}
	long long pw_mod(long long a,long long b,long long M){
		if(a<0LL)return 0;
		if(b<0LL)return 0;
		long long ret=1;
		while(b){
			if(b%2)ret=ret*a%M;
			a=a*a%M;
			b/=2;
		}
		return ret;
	}
	int pw_mod_int(int a,int b,int M){
		if(a<0)return 0;
		if(b<0)return 0;
		int ret=1;
		while(b){
			if(b%2)ret=(long long)ret*a%M;
			a=(long long)a*a%M;
			b/=2;
		}
		return ret;
	}
	int ABS(int a){return max(a,-a);}
	long long ABS(long long a){return max(a,-a);}
	double ABS(double a){return max(a,-a);}
	int sig(double r) { return (r < -EPS) ? -1 : (r > +EPS) ? +1 : 0; }
	int UF[UF_SIZE];
	void init_UF(int n){
		for(int i=0;i<n;i++)UF[i]=-1;
	}
	int FIND(int a){
		if(UF[a]<0)return a;
		return UF[a]=FIND(UF[a]);
	}
	void UNION(int a,int b){
		a=FIND(a);b=FIND(b);if(a==b)return;
		// if(UF[a]>UF[b])swap(a,b);
		UF[a]+=UF[b];UF[b]=a;
	}
}
// ここから編集しろ
char in[1100000];
int S[1100000];

pair<int,int>P[1100000];
int ai[1100000];
int del[1100000];
int cnt[3];
int main(){
	scanf("%s",in);
	int n=strlen(in);
	int m=0;
	for(int i=0;i<n;i++){
		if(i==0||in[i]!=in[i-1]){
			in[m++]=in[i];
		}
	}
	n=m;
	for(int i=0;i<n;i++){
		cnt[in[i]-'A']++;
	}
	int at=0;
	for(int i=1;i<3;i++){
		if(cnt[i]<cnt[at]){
			at=i;
		}
	}
	for(int i=0;i<n;i++){
		S[i]=(in[i]-'A'+3-at)%3;
	}
	int sz=0;
	int B=0;
	int C=0;
	for(int i=0;i<n;i++){
		if(S[i]==0){
			P[sz]=make_pair(B,C);
			B=C=0;
			ai[sz]=i;
			sz++;
		}else{
			if(S[i]==1)B++;
			else C++;
		}
	}
	
	P[sz]=make_pair(B,C);
	sz++;

	int B1=0;
	int B2=0;
	int C1=0;
	int C2=0;
	for(int i=0;i<sz;i++){
		if(P[i].first==0&&P[i].second==0)continue;
		if(P[i].first)B1++;
		else if(0<i&&i+1<sz)C2++;
		if(P[i].second)C1++;
		else if(0<i&&i+1<sz)B2++;
	}
	init_UF(sz+1);
	// printf("%d %d %d %d\n",B1,B2,C1,C2);
	for(int i=0;i<sz-1&&B2>C1;i++){
		int L=FIND(i);
		int R=FIND(i+1);
		if(P[L].second==0&&L!=FIND(0)){
			UNION(R,L);
			B2--;
			if(P[R].first==0){
				C2--;
			}else B1--;
			P[R].first+=P[L].first;
			P[R].second+=P[L].second;
			del[ai[i]]=1;
		}else if(P[R].second==0&&R!=FIND(sz-1)){
			UNION(L,R);
			B2--;
			if(P[L].first==0){
				C2--;
			}else B1--;
			P[L].first+=P[R].first;
			P[L].second+=P[R].second;
			del[ai[i]]=1;
		}
	}
	// printf("%d %d %d %d\n",B1,B2,C1,C2);
	if(B2>C1){
		printf("\n");
	}
	init_UF(sz+1);
	
	for(int i=0;i<sz-1&&C2>B1;i++){
		int L=FIND(i);
		int R=FIND(i+1);
		if(P[L].first==0&&L!=FIND(0)){
			UNION(R,L);
			C2--;
			if(P[R].second==0){
				B2--;
			}else C1--;
			P[R].first+=P[L].first;
			P[R].second+=P[L].second;
			del[ai[i]]=1;
		}else if(P[R].first==0&&R!=FIND(sz-1)){
			UNION(L,R);
			C2--;
			if(P[L].second==0){
				B2--;
			}else C1--;
			P[L].first+=P[R].first;
			P[L].second+=P[R].second;
			del[ai[i]]=1;
		}
	}
	// printf("%d %d %d %d\n",B1,B2,C1,C2);
	if(C2>B1){
		printf("\n");
	}
	m=0;
	for(int i=0;i<n;i++){
		if(del[i]){
			del[i]=0;
			continue;
		}
		if(m==0||S[m-1]!=S[i]){
			S[m++]=S[i];
		}
		
	}
	n=m;
	
	B=C=0;
	for(int i=0;i<n;i++){
		if(S[i]==1)B++;
		if(S[i]==2)C++;
	}
	// printf("%d %d\n",B,C);
	for(int i=0;i<n&&B<C;i++){
		if(S[i]!=2)continue;
		if(i&&i+1<n&&S[i-1]==0&&S[i+1]==0)continue;
		if(i&&i+1<n&&S[i-1]==1&&S[i+1]==1)continue;
		del[i]=1;
		C--;
	}
	for(int i=0;i<n&&C<B;i++){
		if(S[i]!=1)continue;
		if(i&&i+1<n&&S[i-1]==0&&S[i+1]==0)continue;
		if(i&&i+1<n&&S[i-1]==2&&S[i+1]==2)continue;
		del[i]=1;
		B--;
	}
	// printf("%d %d\n",B,C);
	m=0;
	for(int i=0;i<n;i++){
		if(del[i]){
			del[i]=0;
			continue;
		}
		if(m==0||S[m-1]!=S[i]){
			S[m++]=S[i];
		}
		
	}
	n=m;
	int A=0;
	for(int i=0;i<n;i++){
		if(S[i]==0)A++;
	}
	int las=-1;
	for(int i=0;i+1<n&&A<B;i++){
		if(S[i]+S[i+1]==3){
			if(!(las==0&&i+2<n&&S[i+2]==0)){
				B--;
				del[i]=del[i+1]=1;
				i++;
				continue;
			}
		}
		las=S[i];
	}

	m=0;
	for(int i=0;i<n;i++){
		if(del[i]){
			del[i]=0;
			continue;
		}
		if(m==0||S[m-1]!=S[i]){
			S[m++]=S[i];
		}
		
	}
	n=m;
	// assert(n%3==0);
	for(int i=0;i<n;i++){
		printf("%c",'A'+(S[i]+at)%3);
		// assert(i==0||S[i]!=S[i-1]);
	}
	printf("\n");
}

Measured memory_bytes: 16896