#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <ctime>
#include <queue>
using namespace std;
#define MAXN 503

typedef pair< int, int > par;

int A[ MAXN ];
int B[ MAXN ];

int n;

int dist[ MAXN ][ MAXN ];
par prev[ MAXN ][ MAXN ];
queue< par > Q;

queue< char > recon;
queue< char > ret;

vector< int > apotez[ MAXN ];
vector< int > bpotez[ MAXN ];

int main(){
  scanf( "%d", &n );
  for( int i = 0; i < n; ++i ){
    scanf( "%d%d", &A[i], &B[i] );
    --A[i]; --B[i];
    apotez[A[i]].push_back( i );
    bpotez[B[i]].push_back( i );
  }

  memset( dist, 0x3f, sizeof dist );

  dist[0][0] = 0;
  Q.push( par( 0, 0 ) );

  while( !Q.empty() ){
    int x = Q.front().first;
    int y = Q.front().second;
    Q.pop();

    for( int i = 0; i < (int) apotez[x].size(); ++i ){
      for( int j = 0; j < (int) apotez[y].size(); ++j ){
        if( dist[apotez[x][i]][apotez[y][j]] <= dist[x][y] ) continue;
        Q.push( par( apotez[x][i], apotez[y][j] ) );
        dist[apotez[x][i]][apotez[y][j]] = dist[x][y] + 1;
        prev[apotez[x][i]][apotez[y][j]] = par( x, y );
      }
    }

    for( int i = 0; i < (int) bpotez[x].size(); ++i ){
      for( int j = 0; j < (int) bpotez[y].size(); ++j ){
        if( dist[bpotez[x][i]][bpotez[y][j]] <= dist[x][y] ) continue;
        Q.push( par( bpotez[x][i], bpotez[y][j] ) );
        dist[bpotez[x][i]][bpotez[y][j]] = dist[x][y] + 1;
        prev[bpotez[x][i]][bpotez[y][j]] = par( x, y );
      }
    }
  }

  vector< int > sad;
  for( int i = 0; i < n; ++i )
    sad.push_back( i );

  while( (int) sad.size() > 1 ){
    int best = 1;
    for( int i = 2; i < (int) sad.size(); ++i )
      if( dist[0][sad[i]] < dist[0][best] )
        best = i;

    int a = 0, b = sad[best];

    while( a != 0 || b != 0 ){
      par novi = prev[a][b];
      if( A[a] == novi.first ) recon.push( 'A' );
      else recon.push( 'B' );
      a = novi.first;
      b = novi.second;
    }

    while( !recon.empty() ){
      for( int i = 0; i < (int) sad.size(); ++i ){
        if( recon.front() == 'A' ) sad[i] = A[sad[i]];
        else sad[i] = B[sad[i]];
      }
      ret.push( recon.front() );
      recon.pop();
    }

    sort( sad.begin(), sad.end() );
    sad.erase( unique( sad.begin(), sad.end() ), sad.end() );
  }

  for( ; !ret.empty(); ret.pop() ) putchar( ret.front() );
  putchar( '\n' );
  return 0;
}