// gnc type3
#include <iostream>
#include <fstream>
#include <vector>

using namespace std;
struct Coord
{
  int x, y;
  Coord(int a, int b):x(a),y(b){}
};

int ccw(const Coord &c1, const Coord &c2, const Coord &c3)
{
  int x1=c2.x-c1.x, x2 = c3.x-c1.x;
  int y1=c2.y-c1.y, y2 = c3.y-c1.y;
  return x1*y2-x2*y1;
}

int inner_prod(const Coord &c1, const Coord &c2, const Coord &c3)
{
  int x1=c2.x-c1.x, x2 = c3.x-c1.x;
  int y1=c2.y-c1.y, y2 = c3.y-c1.y;
  return x1*x2+y1*y2;
}


int main(void)
{
  int i, j, k, l;
  int x, y;
  int ncoord;
  int rec_area;
  int area;
  int rec[3];
  ifstream fin("myacm.txt");
  while ( fin>>ncoord && ncoord>0) {
    vector<Coord> coords;
    for ( i=0 ; i<ncoord ; i++ ) {
      char c;
      fin>>c>>x>>y;
      coords.push_back(Coord(x,y));
    }
    rec_area = 0;
    for ( i=0 ; i<ncoord ; i++ ) {
      for ( j=i+1 ; j<ncoord ; j++ ) {
        for ( k=j+1 ; k<ncoord ; k++ ) {
          area = ccw(coords[i],coords[j],coords[k]);
          if ( area<0 ) area= -area;
          //cout<<i<<j<<k<<" "<<area<<endl;
          if ( rec_area>area ) continue;
          
          for ( l=0 ; l<ncoord ; l++ ) {
            if ( l==i || l==j || l==k ) continue;
            int c1 = ccw(coords[l],coords[i], coords[j]);
            int c2 = ccw(coords[l],coords[j], coords[k]);
            int c3 = ccw(coords[l],coords[k], coords[i]);
            if ( c1==0 ) {
              if ( inner_prod(coords[l],coords[i],coords[j])>0 )
                continue;
              else
                break;
            }
            if ( c2==0 ) {
              if ( inner_prod(coords[l],coords[j],coords[k])>0 )
                continue;
              else
                break;
            }
            if ( c3==0 ) {
              if ( inner_prod(coords[l],coords[k],coords[i])>0 )
                continue;
              else
                break;
            }
            if ( /*c1*c2*c3==0 ||*/ (c1*c2>0 && c2*c3>0) ) {
              break;
            }
          }
          if ( l!=ncoord ) continue;
          
          rec_area=area;
          rec[0]=i;
          rec[1]=j;
          rec[2]=k;
        }
      }
    }
    cout<<(char)('A'+rec[0])<<(char)('A'+rec[1])<<(char)('A'+rec[2])<<endl;
  }
  return 0;
}