#include <bits/stdc++.h>
#define pb push_back
#define err(x) cerr << #x << " is " << x << '\n';


using namespace std;
typedef double ld;
struct Vector{
    ld x, y;
    Vector(ld x_arg = 0, ld y_arg = 0):x(x_arg), y(y_arg) {}
    friend ostream& operator<<(ostream& os, const Vector& v){
    os << v.x << ' ' << v.y;
    return os;
    }
};
const int MAXN = 1e5;
vector <Vector> fence;
int holes[MAXN / 2], n;
ld hl[MAXN / 2];
ld len(Vector a, Vector b){return sqrt((a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y));}

int main(){
    cout.precision(20);
    int l, k;
    cin >> n >> l >> k;
    for (int i = 0; i < k; i++){
        cin >> holes[i];
        holes[i]--;
    }
    for (int i = 0; i < n; i++){
        int x, y;
        cin >> x >> y;
        fence.pb(Vector(x, y));
    }
    int pos = 0;
    ld l1 = 0, fz = 0;
    for (int i = 0; i < n;i++){
        if (i == holes[pos] && !pos){
            fz = l1;
            pos = (pos + 1) % k;
            l1 = 0;
        }
        else if (i == holes[pos]){
            hl[pos] = l1;
            pos = (pos + 1) % k;
            l1 = 0;
        }
        else{
            l1 += len(fence[i], fence[(i + 1) % n]);
        }
    }
    hl[0] = l1 + fz;
    ld s = 0, ans = 0;
    for (int hole_ind = 0;hole_ind < k;hole_ind++){
        s += len(fence[holes[hole_ind]], fence[(holes[hole_ind] + 1) % n]);
        int ind = hole_ind;
        ld nowl = l, ansn = 0;
        bool flag = false;
        while(nowl > 0 && !(flag && ind == hole_ind)){
            ld tmp = len(fence[holes[ind]], fence[(holes[ind] + 1) % n]);
            if (tmp > nowl){
                ansn += nowl;
                nowl = 0;
            }
            else{
                ansn += tmp;
                nowl -= tmp;
            }
            ind = (ind + 1) % k;
            nowl -= hl[ind];
            flag = true;
        }
        ans = max(ans, ansn);
    }
    cout << s - ans;
}