
#include<iostream>
#include<cmath>
using namespace std;

double dist(double x1,double y1,double x2,double y2){
  return sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
}

int main()
{
  char flag;
  int f;
  double x1,y1,x2,y2,x3,y3,x4,y4,r;
  double x,y;
  while(cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4>>r){
    f=0;
    f += (dist(x1,y1,x4,y4)<r) + (dist(x2,y2,x4,y4)<r) + (dist(x3,y3,x4,y4)<r);
    x=(x1+x2+x3)/3.0;
    y=(y1+y2+y3)/3.0;
    if(f==3)flag='b';
    else if(f)flag='c';
    else if(dist(x,y,x4,y4)<dist(x1,y1,x4,y4))flag='a';
    else flag='d';
    cout<<flag<<endl;
  }
}