static int n, e, x;

static int[][] city;

static ArrayList<int[]>[] list;

static boolean[] visited;

public static void main(String[] args)throws IOException {

BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));

String[] input = buffer.readLine().split(" ");

n = Integer.parseInt(input[0]);

e = Integer.parseInt(input[1]);

x = Integer.parseInt(input[2]);

list = new ArrayList[n+1];

for(int i = 0 ; i <= n ; i++){

list[i] = new ArrayList<>();

}

city = new int[n+1][n+1];

for(int i = 1; i <= n; i++){

Arrays.fill(city[i],Integer.MAX_VALUE/2);

}

for(int i = 0 ; i <e; i++){

input = buffer.readLine().split(" ");

int start = Integer.parseInt(input[0]);

int end = Integer.parseInt(input[1]);

int weight = Integer.parseInt(input[2]);

list[start].add(new int[]{end,weight});

}

for(int k = 1; k <=n; k++){

for(int i = 1; i <=n; i++){

for(int j = 1; j <=n; j++){

city[i][j] = Math.min(city[i][j],city[i][k] + city[k][j]);

}

}

}

for(int i = 1; i<=n; i++) {

dijkstra(i);

}

long max = Integer.MIN_VALUE;

for(int i = 1; i <=n; i++){

max = Math.max(max, city[i][x] + city[x][i]);

}

System.out.println(max);

} // main end

public static void dijkstra(int start){

visited = new boolean[n+1];

city[start][start] = 0;

PriorityQueue<int[]> pqueue = new PriorityQueue<>(Comparator.comparingInt(o->o[1]));

pqueue.offer(new int[] {start, 0});

while(!pqueue.isEmpty()) {

int [] cur = pqueue.poll();

int s = cur[0];

if(visited[s]) continue;

visited[s] = true;

for(int[] now : list[s]){

if(!visited[now[0]]){

if(city[start][now[0]] > city[start][cur[0]]+now[1]){

city[start][now[0]] = city[start][cur[0]]+now[1];

pqueue.offer(new int[]{now[0], city[start][now[0]]});

}

}

}

}// pqeue while end

}