#include<bits/stdc++.h> 
using namespace std;
int a[1200][1200],jl1,jl2,n,m,v;
long long tma=0;
 
int main(){
	freopen("sparty.in","r",stdin);
	freopen("sparty.out","w",stdout);
	cin>>n>>m>>v;
	for (int i=1;i<=n;++i)
	 for (int j=1;j<=n;++j)
	  a[i][j]=10000000;
	for (int i=1;i<=m;++i)
	{
		int x,y,z;
		cin>>x>>y>>z;
		a[x][y]=z;
	}
	for (int k=1;k<=n;++k)
	 for (int i=1;i<=n;++i)
	  if (i!=k)
	   for (int j=1;j<=n;++j)
		if (i!=j)
		{
		 if (a[k][j]+a[i][k]<a[i][j])
		 a[i][j]=a[i][k]+a[k][j];
	    }
	for (int i=1;i<=n;++i)
	 if (i!=v)
	  if (a[i][v]+a[v][i]>tma)
	   tma=a[i][v]+a[v][i];
	cout<<tma;
}