#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("epidemie.in");
ofstream fout("epidemie.out");

int n , a[1005][1005];
int x[1005],
    v[1005],
    d[1005];
int st, dr;

int main()
{
    int i , j, m, k , p;
    fin >> n >> m;
    while(m)
    {
        fin >> i >> j;
        a[i][j] = a[j][i] = 1;
        m --;
    }
    fin >> k;
    for( ; k ; --k)
    {
        fin >> p;
        x[++dr] = p;
        v[p] = d[p] = 1;
    }
    st = 1;
    while(st <= dr)
    {
        int k = x[st];
        for(int i = 1; i <= n ; ++i)
            if(v[i] == 0 && a[k][i] == 1)
            {
                dr ++;
                v[i] = 1;
                x[dr] = i;
                d[i] = d[k] + 1;
            }
        st ++;
    }
    int C = 0;
    for(int i = 1 ; i <= n ; ++i)
        if(d[i] > C)
            C = d[i];
    fout << C;
    return 0;
}