#include <stdio.h>
#include<fstream>
using namespace std;
ifstream f ("ubuntzei.in");
ofstream g ("ubuntzei.out");

int n, a[2005][2005],m,pr[2000],k;

void citire()
{
	int i,c,b,d;
	f>>n>>m>>k;
	for ( i=1; i<=k; i++ )
		f>>pr[i];
	for (i =1; i<=n; i++)
	{
		f>>b>>c>>d;
		a[b][c]=d;
		a[c][b]=d;
	}
		
}

void roy_floyd()
{
	int i, j, k;
	for (k = 1; k <= n; k++)
		for (i =1; i <= n; i++)
			for (j = 1; j <= n; j++)
				if (a[i][k] && a[k][j] && (a[i][j] > a[i][k] + a[k][j] || !a[i][j]) && i != j) 
					a[i][j] = a[i][k] + a[k][j];
}

void afisare()
{
	
	g<<a[1][n];
}


int main()
{
	citire();
	roy_floyd();
	afisare();
	
}