#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>

using namespace std;

const int MAXN=1010;
const int MAXM=300000;
const int M=2000;
const int oo=1000000000;

struct edge
{
	int t,c;
	edge *p;
}e[MAXM],*v[MAXN],fe[MAXM],*fv[MAXN];

int dis1[MAXN],dis2[MAXN],es=-1,n,m,i,j,k,S,ans,q[MAXN*5],h,t,s;
bool iq[MAXN];

inline void addedge(int i,int j,int c)
{
	e[++es].t=j; e[es].c=c; e[es].p=v[i]; v[i]=e+es;
	fe[es].t=i; fe[es].c=c; fe[es].p=fv[j]; fv[j]=fe+es;
}

void init()
{
	freopen("party.in","r",stdin);
	freopen("party.out","w",stdout);
	scanf("%d%d%d",&n,&m,&S);
	for (i=1;i<=m;i++)
	{
		scanf("%d%d%d",&j,&k,&t);
		addedge(j,k,t);
	}
}

void spfa(edge *e,edge **v,int *dis)
{
	memset(iq,false,sizeof(iq));
	for (i=1;i<=n;i++)
		dis[i]=oo;
	dis[S]=0;
	h=t=s=1;
	iq[S]=true;
	q[1]=S;
	while (s)
	{
		k=q[h];
		for (edge *x=v[k];x;x=x->p)
			if (dis[x->t]>dis[k]+x->c)
			{
				dis[x->t]=dis[k]+x->c;
				if (!iq[x->t])
				{
					++s;
					t=(t+1)%M;
					q[t]=x->t;
					iq[x->t]=true;
				}
			}
		iq[k]=false;
		h=(h+1)%M;
		--s;
	}
}

void solve()
{
	spfa(e,v,dis1);
	spfa(fe,fv,dis2);
	for (i=1;i<=n;i++)
		if (dis1[i]+dis2[i]>ans) ans=dis1[i]+dis2[i];
	printf("%d\n",ans);
}

int main()
{
	init();
	solve();
	return 0;
}