#include<iostream>
using namespace std;

int arr[1002][1002], dist[1002], go[1002];
bool sp[1002];
int N, M, X;
void dijks(int start){
  for(int i = 1; i<= N; i++){
    sp[i] = false;
    dist[i] = -1;
    if(i == start){
      dist[i] = 0;
    }
  }
  int now = start;
  sp[now] = true;
  dist[now] = 0;
  for(int k = 1; k< N; k++ ){
    for(int i = 1; i<= N; i++){
      if(arr[now][i] == -1 || sp[i] == true){

      }
      else if(dist[i] == -1 || dist[i] > dist[now] + arr[now][i]){
        dist[i] = dist[now] + arr[now][i];
        //cout<< i << " " << dist[i] << " " << dist[now] << " " << arr[now][i]<< endl;
      }
      //cout<< now << " "<< i << " " << dist[i]<< " " << arr[now][i]<< endl;
    }
    int min = -1;
    for(int i = 1; i<= N; i++){
      if(sp[i] == false && dist[i] != -1 && (min == -1 || dist[min] > dist[i]))
        min = i;
    }
    now = min;
    sp[now] = true;
  }
  /*for(int i = 1; i<= N; i++){
    cout<<i <<" " <<dist[i] << endl;
  }*/
}
void gototown(int start){
  for(int i = 1; i<= N; i++){
    sp[i] = false;
    go[i] = -1;
    if(i == start){
      go[i] = 0;
    }
  }
  int now = start;
  sp[now] = true;
  go[now] = 0;
  for(int k = 1; k< N; k++ ){
    for(int i = 1; i<= N; i++){
      if(arr[i][now] == -1 || sp[i] == true){

      }
      else if(go[i] == -1 || go[i] > go[now] + arr[i][now]){
        go[i] = go[now] + arr[i][now];
        //cout<< i << " " << dist[i] << " " << dist[now] << " " << arr[now][i]<< endl;
      }
      //cout<< now << " "<< i << " " << dist[i]<< " " << arr[now][i]<< endl;
    }
    int min = -1;
    for(int i = 1; i<= N; i++){
      if(sp[i] == false && go[i] != -1 && (min == -1 || go[min] > go[i]))
        min = i;
    }
    now = min;
    sp[now] = true;
  }
  /*for(int i = 1; i<= N; i++){
    cout<<i <<" " <<dist[i] << endl;
  }*/
}
int main(){
    cin>> N >> M >> X;
    for(int i = 1; i<=N; i++){
      for(int j = 1; j<= N; j++){
        arr[i][j] = -1;
      }
    }
    for(int i = 0; i<M; i++){
      int s, e, t;
      scanf("%d %d %d", &s, &e, &t);
      arr[s][e] = t;
    }

    gototown(X);
    dijks(X);
    int max = 0;
    for(int i = 1; i<= N; i++){
      if(max < go[i] + dist[i]){
        //cout << i << " " << go[i] << " " << dist[i];
        max = go[i] + dist[i];
      }
    }
    cout << max;

}

#include <iostream>
#define MAX_INT 217483647
using namespace std;
 
int edge[1001][1001], dist[2][1001];
bool visit[2][1001];
 
int main()
{
    int n, m, s, i, j;
    //입력 및 초기화
    cin >> n >> m >> s;
    for (i = 0; i<m; i++)
    {
        int a, b, c;
        cin >> a >> b >> c;
        edge[a][b] = c;
    }
    for (i = 0; i <= n; i++)
    {
        visit[0][i] = false, visit[1][i] = false;
        dist[0][i] = MAX_INT, dist[1][i] = MAX_INT;
    }
    //첫번째도 두번째도 시작점에서 dist = 0
    dist[0][s] = 0, dist[1][s] = 0;
    for (i = 0; i<n; i++)
    {
        int min1 = 0, min2 = 0;
        //min1,min2값 탐색
        for (j = 1; j <= n; j++)
        {
            if (visit[0][j] == false && dist[0][min1]>dist[0][j]) min1 = j;
            if (visit[1][j] == false && dist[1][min2]>dist[1][j]) min2 = j;
        }
        //visit check
        visit[0][min1] = true;
        visit[1][min2] = true;
        //경로 탐색
        for (j = 1; j <= n; j++)
        {
            //기존 dijkstra와 동일
            if (dist[0][j]>dist[0][min1] + edge[min1][j] && edge[min1][j] != 0) dist[0][j] = dist[0][min1] + edge[min1][j];
            //반대로 edge를 먼저 생각하고 dist를 생각한다.
            if (dist[1][j]>edge[j][min2] + dist[1][min2] && edge[j][min2] != 0) dist[1][j] = edge[j][min2] + dist[1][min2];
        }
    }
    //최댓값 탐색
    int res = 0;
    for (i = 1; i <= n; i++)
    {
        if (res<dist[0][i] + dist[1][i] && dist[0][i] != MAX_INT && dist[1][i] != MAX_INT) res = dist[0][i] + dist[1][i];
    }
    //출력
    cout << res;
    return 0;
}