#include <bits/stdc++.h>
#define INF 0x3F3F3F3F
#define N 2001
#define K 16
using namespace std;

array <array <bitset <K>, N>, N> dp; //wtf
array <vector <pair <int, int>>, N> G;
bitset <N> seen;
bitset <K> left;

int main () {
    ifstream fin ("ubuntzei.in");
    ofstream fout ("ubuntzei.out");
    int n, m, k, i, j, c;
    fin >> n >> m
        >> k;
    for (; k; k--) {
        fin >> i;
        left[i]=1;
    }
    fin.close();

    if (!k) {
        Dijkstra(1);
        fout << dp[1][to_string(n)] << endl;
        fout.close();
        return 0;
    }

    for (i=1; i<K; i++)
        if (left[i])
            Dijkstra(i);
    for (auto it: dp)
        it.fill(INF);

    return 0;
}