Language: C++

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <ctime>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <cstring>
#include <vector>
#include <algorithm>
#include <functional>
#include <fstream>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstring>
#include <numeric>
#include <cassert>
using namespace std;
static const double EPS = 1e-8;
typedef long long ll;
#define rep(i,n) for(int i=0;i<n;i++)
#define rev(i,n) for(int i=n-1;i>=0;i--)
#define all(a) a.begin(),a.end()
#define mp(a,b) make_pair(a,b)
#define pb(a) push_back(a)
#define SS stringstream
#define DBG1(a) rep(_X,sz(a)){printf("%d ",a[_X]);}puts("");
#define DBG2(a) rep(_X,sz(a)){rep(_Y,sz(a[_X]))printf("%d ",a[_X][_Y]);puts("");}
#define bitcount(b) __builtin_popcount(b)
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)

typedef complex<double> P;
struct L : public vector<P> {L(const P &a, const P &b) {push_back(a); push_back(b);} };

int chk(P a,P b,double r){
	double t = abs(a-b) - r;
	if( fabs(t) < EPS ) return 0;
	return t < 0 ? -1 : 1;
}
double cross(P a,P b){
	return imag(a*conj(b));
}
double dot(const P& a, const P& b) {return real(conj(a)*b);}



P projection(const L &l, const P &p) {double t = dot(p-l[0], l[0]-l[1]) / norm(l[0]-l[1]);return l[0] + t*(l[0]-l[1]);}

bool intersectSP(const L &s, const P &p) {return abs(s[0]-p)+abs(s[1]-p)-abs(s[1]-s[0]) < EPS;}

double distanceSP(const L &s, const P &p) {
	const P r = projection(s, p);
	if (intersectSP(s, r)) return abs(r - p);
	return min(abs(s[0] - p), abs(s[1] - p));
}

int main(){
	P a,b,c,d;
	double r;
	while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
		cin >> b.real() >> b.imag();
		cin >> c.real() >> c.imag();
		cin >> d.real() >> d.imag();
		cin >> r;
		
		int in = 0;
		int mk = cross(a-d,b-d) <= 0 ;
		if( mk == (cross(b-d,c-d) <= 0) && mk == (cross(c-d,a-d) <= 0)){
			in = 1;
		}
		
		if( chk(a,d,r) <= 0 &&  chk(b,d,r) <= 0 &&  chk(c,d,r) <= 0 ){
			cout << "b" << endl;
		}else if( chk(a,d,r) >= 0 &&  chk(b,d,r) >= 0 &&  chk(c,d,r) >= 0){
			if( distanceSP(L(a,b),d) < r - EPS || distanceSP(L(b,c),d) < r - EPS || distanceSP(L(a,c),d) < r - EPS  ){
				cout << "c" << endl;
			}else if( in ){
				cout << "a" << endl;
			}else if( distanceSP(L(a,b),d) > r + EPS || distanceSP(L(b,c),d) > r + EPS || distanceSP(L(a,c),d) > r + EPS )
				cout << "d" << endl;
			}
			cout << "c" << endl;
		}else{
			cout << "c" << endl;
		}
	

		
	}
}

Compiler output:
a.cc: In function 'int main()':
a.cc:67:19: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'double')
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |               ~~~ ^~ ~~~~~~~~
      |               |            |
      |               |            double
      |               std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:10:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'double&' to an rvalue of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:7: note:   conversion of argument 1 would be ill-formed:
a.cc:67:28: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'double'
   67 |         while(cin >> a.real() >> a.imag() , a.real() != 0 || a.imag() != 0 ){
      |                      ~~~~~~^~
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:25: note:   no known conversion for argument 1 from 'double' to 'void*&'
  328 |       operator>>(void*& __p)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'double' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]'
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:32: note:   no known conversion for argument 1 from 'double' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_i