боевой

#include <iostream>
#include <vector>
#include <cmath>

const int INF = 1000000007;

struct agent
{
    int x;
    int y;
};

double dist(agent A, agent B)
{
    int x = A.x - B.x;
    int y = A.y - B.y;
    return sqrt(x * x + y * y);
}

int main()
{
    int n, x, y;
    std::cin >> n;
    std::vector<struct agent> agents(n);
    std::vector<std::vector<double> > g(n, std::vector<double>(n));

    for (int i = 0; i < n; ++i)
        std::cin >> agents[i].x >> agents[i].y;

    for (int i = 0; i < n; ++i)
        for (int j = i + 1; j < n; ++j)
        {
            double d = dist(agents[i], agents[j]);
            g[i][j] = d;
            g[j][i] = d;
        }


    std::vector<bool> used(n);
    std::vector<double> min_e(n, INF);

    min_e[0] = 0;
    double R = 0;

    for (int i = 0; i < n; ++i)
    {
        int v = -1;
        for (int j = 0; j < n; ++j)
            if (!used[j] && (v == -1 || min_e[j] < min_e[v]))
                v = j;

        if (R < min_e[v])
            R = min_e[v];

        used[v] = true;
        for (int to = 0; to < n; ++to)
            if (g[v][to] < min_e[to])
                min_e[to] = g[v][to];
    }

    std::cout << R;
    return 0;
}