Language: C++

#include <bits/stdc++.h>

#define _overload(_1,_2,_3,name,...) name
#define _rep(i,n) _range(i,0,n)
#define _range(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload(__VA_ARGS__,_range,_rep,)(__VA_ARGS__)

#define _rrep(i,n) _rrange(i,n,0)
#define _rrange(i,a,b) for(int i=int(a)-1;i>=int(b);--i)
#define rrep(...) _overload(__VA_ARGS__,_rrange,_rrep,)(__VA_ARGS__)

#define _all(arg) begin(arg),end(arg)
#define uniq(arg) sort(_all(arg)),(arg).erase(unique(_all(arg)),end(arg))
#define getidx(ary,key) lower_bound(_all(ary),key)-begin(ary)
#define clr(a,b) memset((a),(b),sizeof(a))
#define bit(n) (1LL<<(n))
#define popcount(n) (__builtin_popcountll(n))

using namespace std;

template<class T>bool chmax(T &a, const T &b) { return (a<b)?(a=b,1):0;}
template<class T>bool chmin(T &a, const T &b) { return (b<a)?(a=b,1):0;}

using ll=long long;
using R=long double;
const R EPS=1e-9L; // [-1000,1000]->EPS=1e-8 [-10000,10000]->EPS=1e-7
inline int sgn(const R& r){return(r > EPS)-(r < -EPS);}
inline R sq(R x){return sqrt(max(x,0.0L));}

const int dx[8]={1,0,-1,0,1,-1,-1,1};
const int dy[8]={0,1,0,-1,1,1,-1,-1};

// Problem Specific Parameter:

// Description: ????????????
// Verifyed: various problem 
const R INF = 1E40L;
const R PI = acos(-1.0L);
using P=complex<R>;
const P O=0.0L;
using L=struct{P s,t;};
using VP=vector<P>;
using C=struct{P c;R r;};

istream& operator >> (istream& is,P& p){ R x,y;is >> x >> y; p=P(x,y); return is;}
ostream& operator << (ostream& os,P& p){ os << real(p) << " " << imag(p); return os;}

inline R dot(P o,P a,P b){return real(conj(a-o)*(b-o));}
inline R det(P o,P a,P b){return imag(conj(a-o)*(b-o));}
inline int sdot(P o,P a,P b){return sgn(dot(o,a,b));}
inline int sdet(P o,P a,P b){return sgn(det(o,a,b));}

//projection verify AOJ CGL_1_A
P proj(L l,P p){ R u=real((p-l.s)/(l.t-l.s)); return (1-u)*l.s+u*l.t;}

// cross point between circle and line 
// verified: AOJ CGL_7_D
P cir(C c,R t){return c.c+polar(c.r,t);}
VP cross(C c, L l){
	P h=proj(l,c.c),e=polar(sq(norm(c.r)-norm(h-c.c)),arg(l.t-l.s));
	return VP{h-e,h+e};
}

// cross point between circles
// verified: AOJ CGL_7_E
VP cross(C a,C b){
	P d=b.c-a.c,w=(norm(d)+norm(a.r)-norm(b.r))/(2.0*norm(d))*d;
	return cross(a,{a.c+w,a.c+w+1iL*w});
}


int main(void){
	int q;
	C c1,c2;
	cin >> c1.c >> c1.r >> c2.c >> c2.r;
		
	VP res=pcc(c1,c2);
	if(sgn(real(res[0])-real(res[1])>0)) swap(res[0],res[1]);
	if(sgn(real(res[0])-real(res[1]))==0 and sgn(imag(res[0])-imag(res[1]))>0) swap(res[0],res[1]);
	cout.precision(20);
	cout << fixed << res[0] << " " << res[1] << endl;
	return 0;
}

Compiler output:
a.cc: In function 'VP cross(C, C)':
a.cc:68:40: error: no match for 'operator*' (operand types are '__complex__ long int' and 'P' {aka 'std::complex<long double>'})
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                     ~~~^~
      |                                     |   |
      |                                     |   P {aka std::complex<long double>}
      |                                     __complex__ long int
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:1:
/usr/include/c++/14/complex:400:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const complex<_Tp>&)'
  400 |     operator*(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:400:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::complex<_Tp>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/complex:409:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const complex<_Tp>&, const _Tp&)'
  409 |     operator*(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:409:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::complex<_Tp>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/complex:418:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator*(const _Tp&, const complex<_Tp>&)'
  418 |     operator*(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:418:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   deduced conflicting types for parameter '_Tp' ('__complex__ long int' and 'long double')
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   'P' {aka 'std::complex<long double>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/bits/valarray_after.h:407:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__multiplies, typename _Dom1::value_type>::result_type> std::operator*(const valarray<typename _Dom::value_type>&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  407 |     _DEFINE_EXPR_BINARY_OPERATOR(*, struct std::__multiplies)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:407:5: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   'P' {aka 'std::complex<long double>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::valarray<_Tp>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   mismatched types 'const std::valarray<_Tp>' and '__complex__ long int'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
/usr/include/c++/14/valarray:1198:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__multiplies, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__multiplies, _Tp>::result_type> std::operator*(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)'
 1198 | _DEFINE_BINARY_OPERATOR(*, __multiplies)
      | ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/valarray:1198:1: note:   template argument deduction/substitution failed:
a.cc:68:41: note:   'P' {aka 'std::complex<long double>'} is not derived from 'const std::valarray<_Tp>'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                                         ^
a.cc:68:21: error: no matching function for call to 'cross(C&, <brace-enclosed initializer list>)'
   68 |         return cross(a,{a.c+w,a.c+w+1iL*w});
      |                ~~~~~^~~~~~~~~~~~~~~~~~~~~~~
a.cc:59:4: note: candidate: 'VP cross(C, L)'
   59 | VP cross(C c, L l){
      |    ^~~~~
a.cc:59:17: note:   no known conversion for argument 2 from '<brace-enclosed initializer list>' to 'L' {aka '<unnamed struct>'}
   59 | VP cross(C c, L l){
      |               ~~^
a.cc:66:4: note: candidate: 'VP cross(C, C)'
   66 | VP cross(C a,C b){
      |    ^~~~~
a.cc:66:16: note:   no known conversion for argument 2 from '<brace-enclosed initializer list>' to 'C' {aka '<unnamed struct>'}
   66 | VP cross(C a,C b){
      |              ~~^
a.cc: In function 'int main()':
a.cc:77:16: error: 'pcc' was not declared in this scope
   77 |         VP res=pcc(c1,c2);
      |                ^~~