#define _USE_MATH_DEFINES
#include<stdio.h>
#include<iostream>
#include<vector>
#include<cmath>
#include<algorithm>
#include<memory.h>
#include<map>
#include<set>
#include<queue>
#include<list>
#include<sstream>
#include<cstring>
#include<numeric>
#include<limits.h>
using namespace std;

const int N = 1e5;

struct point{
private:
    double x, y;
public:
    point() {}
    point(double x, double y) : x(x), y(y) {}
    void scan() {
        scanf("%lf%ld", &x, &y);
    }
    point operator-(const point & A) const {
        return point(x - A.x, y - A.y);
    }

    double operator* (const point & A) const {
        return x * A.y - y * A.x;
    }

    double operator% (const point & A) const {
        return x * A.x + y * A.y;
    }

    double dist(const point & A) const {
        point r = A - *this;
        return r.val();
    }

    double val() {
        return hypot(x, y);
    }



} a[N];


int main(){
    int n;
    scanf("%d", &n);
    point P;
    P.scan();
    for (int i = 0; i < n; i++) {
        a[i].scan();
    }
    a[n] = a[0];
    bool minus = false;
    bool plus = false;
    double res = 1e12;
    for (int i = 0; i<n; i++)
    {
        double val = (a[i] - P) * (a[i + 1] - P);
        if ((P - a[i]) % (a[i + 1] - a[i]) < 0)
            res = min(res, a[i].dist(P));
        else {
            res = min(res, ((P - a[i + 1]) % (a[i] - a[i + 1])) < 0 ?
                a[i + 1].dist(P) :
                abs(val) / ((a[i] - a[i + 1]).val())
                );
        }
        if (val > 0)
            plus = true;
        else
            if (val < 0)
                minus = true;
    }
    if (!(plus && minus))
    {
        printf("0.000");
        return 0;
    }
    printf("%.3lf", res * 2);
    return 0;
}