Language: C++

#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
/*
    s.find_by_order(k) ---> returns iterator to the element at index(from 0) k
    s.order_of_key(val) ---> number of elements that are strictly smaller than the given value
*/
typedef long long int ll;
typedef unsigned long long ull;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long int> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long int>> vvl;
typedef pair<int, int> pii;
typedef pair<long long int, long long int> pll;
typedef vector<pair<int, int>> vii;
typedef vector<pair<long long int, long long int>> vll;
#define fast() ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define test() long long int tc; cin >> tc; cin.ignore(); while(tc--) 
#define ff first
#define ss second
#define pb push_back
#define pf push_front
#define mp make_pair
#define MOD 1000000007
#define SMOD 998244353
#define pq priority_queue
#define all(x) x.begin(),x.end()
#define SP(x) setprecision(x)
#define sp " "
#define inp(a) ll a;cin>>a;cin.ignore()
#define inps(a,b) ll a,b;cin>>a>>b;cin.ignore()
#define out(a) cout<<SP(20)<<a<<'\n'
#define outs(a,b) cout<<SP(20)<<a<<" "<<b<<'\n'
#define ins insert
#define er erase
#define lb lower_bound
#define ub upper_bound
#define printclock cerr<<"Time : "<<1000*(ld)clock()/(ld)CLOCKS_PER_SEC<<"ms\n";
#define inpa(a,n) ll a[n]; for(int i=0; i<n; i++){cin>>a[i];}
#define inpv(a,n) vl a; for(int i=0; i<n; i++){inp(x);a.pb(x);}
#define outa(a,n) for(int i=0;i<n;i++){cout<<a[i]<<" ";}cout<<'\n';
#define outv(v) for(auto i:v){cout<<i<<" ";}cout<<'\n';
set<char> vow = {'a','e','i','o','u','A','E','I','O','U'};
ll xpow(ll n, ll m){if(m==0){return 1;}else{ll x = xpow(n, m/2);if(m&1){return x*x*n;}else{return x*x;}}}
ll xmod(ll a, ll m){return (((a%m)+m)%m);}
ll xmodpow(ll n, ll m, ll y){if(m==0){return 1;}else{ll x = xmodpow(n, m/2, y);if(m&1){return xmod((xmod((xmod(x,y)*xmod(x,y)),y)*xmod(n,y)),y);}else{return xmod((xmod(x,y)*xmod(x,y)),y);}}}

ld X, Y, rad;

void findCircle(ld x1, ld y1, ld x2, ld y2, ld x3, ld y3) 
{ 
    ld x12 = x1 - x2; 
    ld x13 = x1 - x3; 
    ld y12 = y1 - y2; 
    ld y13 = y1 - y3; 
    ld y31 = y3 - y1; 
    ld y21 = y2 - y1; 
    ld x31 = x3 - x1; 
    ld x21 = x2 - x1; 
    ld sx13 = pow(x1, 2) - pow(x3, 2); 
    ld sy13 = pow(y1, 2) - pow(y3, 2); 
    ld sx21 = pow(x2, 2) - pow(x1, 2); 
    ld sy21 = pow(y2, 2) - pow(y1, 2); 
    ld f = ((sx13) * (x12) 
             + (sy13) * (x12) 
             + (sx21) * (x13) 
             + (sy21) * (x13)) 
            / (2 * ((y31) * (x12) - (y21) * (x13))); 
    ld g = ((sx13) * (y12) 
             + (sy13) * (y12) 
             + (sx21) * (y13) 
             + (sy21) * (y13)) 
            / (2 * ((x31) * (y12) - (x21) * (y13))); 
  
    ld c = -pow(x1, 2) - pow(y1, 2) - 2 * g * x1 - 2 * f * y1; 
    ld h = -g; 
    ld k = -f; 
    ld sqr_of_r = h * h + k * k - c; 
    ld r = sqrt(sqr_of_r); 
    X = h;
    Y = k;
    rad = r;
} 

int n;
long double x[1005], y[1005], X, Y, d, e;
long double dist(long double a, long double b) {
	return a*a + b*b;
}
int main() {
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		scanf("%Lf%Lf", &x[i], &y[i]);
		X += x[i]; Y += y[i];
	}
	X /= n; Y /= n;
	double P = 0.1;
	for (int i = 0; i < 30000; i++) {
		int f = 0;
		d = dist(X - x[0], Y - y[0]);
		for (int j = 1; j < n; j++) {
			e = dist(X - x[j], Y - y[j]);
			if (d < e) { d = e; f = j; }
		}
		X += (x[f] - X)*P;
		Y += (y[f] - Y)*P;
		P *= 0.999;
	}
	printf("%.15Lf\n", (long double)sqrt(d));
}

Compiler output:
a.cc:92:31: error: redefinition of 'long double X'
   92 | long double x[1005], y[1005], X, Y, d, e;
      |                               ^
a.cc:54:4: note: 'ld X' previously declared here
   54 | ld X, Y, rad;
      |    ^
a.cc:92:34: error: redefinition of 'long double Y'
   92 | long double x[1005], y[1005], X, Y, d, e;
      |                                  ^
a.cc:54:7: note: 'ld Y' previously declared here
   54 | ld X, Y, rad;
      |       ^