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

using namespace std;

const int oo=1000000000;
int n,m,x;
int w[1001][1001];
int f[1001],g[1001];
bool y[1001];

int main()
{
	freopen("party.in","r",stdin);
	freopen("party.out","w",stdout);
	scanf("%d%d%d",&n,&m,&x);
	int a,b,t;
	for (int i=1;i<=n;i++)
	for (int j=1;j<=n;j++)
	{
		w[i][j]=oo;
	}
	for (int i=1;i<=m;i++)
	{
		scanf("%d%d%d",&a,&b,&t);
		w[a][b]=min(w[a][b],t);
	}
	
	for (int i=1;i<=n;i++) f[i]=oo,g[i]=oo;
	f[x]=0;g[x]=0;
	int now=x;int minn=0;
	while (minn!=oo)
	{
		y[now]=true;
		minn=oo;
		for (int i=1;i<=n;i++)
		if (!y[i])
		{
			if (f[i]>w[now][i]+f[now]) f[i]=f[now]+w[now][i];
		}
		for (int i=1;i<=n;i++)
		if (!y[i])
		{
			if (f[i]<minn) minn=f[i],now=i;
		}
	}
	memset(y,0,sizeof(y));
	minn=0,now=x;
	while (minn!=oo)
	{
		y[now]=true;
		minn=oo;
		for (int i=1;i<=n;i++)
		if (!y[i])
		{
			if (g[i]>w[i][now]+g[now]) g[i]=g[now]+w[i][now];
		}
		for (int i=1;i<=n;i++)
		if (!y[i])
		{
			if (g[i]<minn) minn=g[i],now=i;
		}
	}
	int ans=0;
	for (int i=1;i<=n;i++)
	if (f[i]+g[i]<oo)
	{
		if (f[i]+g[i]>ans) ans=f[i]+g[i];
	}
	printf("%d\n",ans);
	return 0;
}