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OI-codes/AtCoder/ABC255/B/B.cpp

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#include <iostream>
#include <cmath>
#include <iomanip>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1005;
int n, k, a[N];
bool has[N];
std::pair<int, int> points[N];
double dis[N][N], dist[N], ans;
double getdis(std::pair<int, int> a, std::pair<int, int> b) {
return std::sqrt(1ll * (a.first - b.first) * (a.first - b.first) + 1ll * (a.second - b.second) * (a.second - b.second));
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> k;
for (int i = 1; i <= k; i++) {
cin >> a[i];
has[a[i]] = true;
}
for (int i = 1; i <= n; i++) {
cin >> points[i].first >> points[i].second;
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j < i; j++) {
dis[i][j] = dis[j][i] = getdis(points[i], points[j]);
}
}
for (int i = 1; i <= n; i++) {
if (!has[i]) {
dist[i] = 9999999999;
for (int j = 1; j <= n; j++) {
if (i != j) {
if (has[j]) {
dist[i] = std::min(dist[i], dis[i][j]);
}
}
}
}
}
for (int i = 1; i <= n; i++) {
ans = std::max(ans, dist[i]);
}
cout << std::fixed << std::setprecision(10) << ans << endl;
return 0;
}