task628

#include <iostream>
#include <algorithm>
#include <vector>
#include <math.h>

using namespace std;

long double len(vector <vector <int>> &a, int x) {

    long double sum = 0;

    for (int i = 0; i < a.size(); i++)
        sum += sqrt(   1LL * (a[i][0] - x) * (a[i][0] - x) +  1LL * (a[i][1]) * (a[i][1])    );

    return sum;

}

int main() {

    int n;
    cin >> n;


    vector <vector <int>> a(n-2, vector <int>(2));

    int x1, y1, x2, y2;
    cin >> x1 >> y1 >> x2 >> y2;

    if (n == 2) {
        cout << x1;
        return 0;
    }

    for (int i = 0; i < n - 2; i++) {
        cin >> a[i][0];
        cin >> a[i][1];
    }

    int l = min(x1, x2);
    int r = max(x1, x2);


    while (r - l > 3) {
        int m1 = l + (r - l) / 3;
        int m2 = r - (r - l) / 3;

        if (len(a, m1) > len(a, m2))
            l = m1;
        else if (len(a, m1) < len(a, m2))
            r = m2;
        else {
            l = m1;
            r = m2;
        }
    }


    vector <long double> b(5);

    b[0] = len(a, x1);
    b[1] = len(a, l);
    b[2] = len(a, l + 1);
    b[3] = len(a, r);
    b[4] = len(a, x2);

    long double min = b[0];

    for (int i = 1; i < b.size(); i++)
        if (min > b[i])
            min = b[i];
    cout << min;
    return 0;
}