#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

//int INF=(1<<31)-1;

//int mi=-(1<<31)+1;

#define read(x) scanf("%d",&x);

#define fo(i,n) for(int i=0;i<(n);i++)

#define one(x) cout<<(x)<<endl;

#define two(a,b) cout<<(a)<<" "<<(b)<<endl;

int main()

{

	ios::sync_with_stdio(false);

	string s;

	cin>>s;

	if(s.find("AB")!=-1&&s.find("BA",s.find("AB")+2)!=-1||s.find("BA")!=-1&&s.find("AB",s.find("BA")+2)!=-1)

	cout<<"YES"<<endl;

	else

	cout<<"NO"<<endl;

	return 0;

}