#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<cstring>

#include<cmath>

#include<queue>

#include<vector>

using namespace std;

const int maxn=1000+1,maxm=100000+1,INF=1e+8;

int len[maxn][maxn],len1[maxn][maxn],dist[maxn],dist1[maxn];

vector<int> path[maxn],path1[maxn];

int n,m,source;

void SPFA(int dist[],int d[][maxn],vector<int>son[],int source)

{

 bool inq[maxn];

 int times[maxn];

 memset(inq,0,sizeof(inq));

 memset(times,0,sizeof(times));

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

 	dist[i]=INF;

 dist[source]=0;

 queue<int>q;

 q.push(source);

 times[source]++;

 inq[source]=true;

 while(!q.empty())

 	{

 	 int now=q.front();

	 q.pop();

	 inq[now]=false;

	 for(int i=0;i<son[now].size();i++)

	 	{

	 	 int np=son[now][i];

	 	 if(dist[np]>dist[now]+d[now][np])

	 	 	{

	 	 	 dist[np]=dist[now]+d[now][np];

	 	 	 if(times[np]>n)return;

	 	 	 if(!inq[np]){times[np]++;q.push(np);}

			}

		}

	}

}

int main()

{freopen("t.txt","r",stdin);

 scanf("%d%d%d",&n,&m,&source);

 for(int i=0;i<m;i++)

 	{

 	 int a,b,l;

 	 scanf("%d%d%d",&a,&b,&l);

 	 path[a].push_back(b);len[a][b]=l;

 	 path1[b].push_back(a);len1[b][a]=l;

	}

 SPFA(dist,len,path,source);

 SPFA(dist1,len1,path1,source);

 int ans=0;

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

 	{

 	 if((dist[i]+dist1[i])>ans)ans=dist[i]+dist1[i];

	}

 printf("%d\n",ans);

 return 0;

}