#include<bitset>
#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<cstring>
#include <vector>
#include <queue>
using namespace std;
typedef long long ll;
const int INF=1e9;
const int MAX_V=1000+7;
const int MAX_E=100000+7;
int m,t,x,ans;
struct edge{
	int to,cost;
};
typedef pair<int,int> P;
int V;
vector<edge> G[MAX_V];
int d[MAX_V];
int data1[MAX_V],data2[MAX_V];
void dijkstra(int s){
	priority_queue<P,vector<P>,greater<P> > que;
	fill(d,d+V+1,INF);
	d[s]=0;
	que.push(P(0,s));
	while (!que.empty())
	{
		P p=que.top();que.pop();
		int v=p.second;
		if(d[v]<p.first)continue;
		for (unsigned int i = 0; i < G[v].size(); i += 1)
		{
			edge e=G[v][i];
			if(d[e.to]>d[v]+e.cost){
				d[e.to]=d[v]+e.cost;
				que.push(P(d[e.to],e.to));
			}
		}
	}
}
int main()
{
	scanf("%d%d%d",&V,&m,&x);
	int a;edge ex;
	for (int i = 0; i < m; i += 1)
	{
		scanf("%d%d%d",&a,&ex.to,&ex.cost);
		G[a].push_back(ex);
	}
	dijkstra(x);
	for (int i = 1; i <= V; i += 1)data1[i]=d[i];
	for (int i = 1; i <= V; i += 1){dijkstra(i);data2[i]=d[x];}
	for (int i = 1; i <= V; i += 1)ans=max(ans,data1[i]+data2[i]);
	printf("%d\n",ans);
	return 0;
}