#include<bits/stdc++.h>
#define int long long
#define INF 0x3f3f3f
using namespace std;
int n,x,m,max_=-1;
int a[4001],b[4001],c[4001];
int f[4001][4001];
signed main()
{
	cin>>n>>m>>x;
	memset(f,INF,sizeof(f));
	for(int i=1;i<=n;i++)
		f[i][i]=0;
	for(int i=1;i<=m;i++){
		cin>>a[i]>>b[i]>>c[i];
		f[a[i]][b[i]]=min(f[a[i]][b[i]],c[i]);
	}
	for(int k=1;k<=n;k++)
	for(int i=1;i<=n;i++)
	for(int j=1;j<=n;j++)
		f[i][j]=min(f[i][j],f[i][k]+f[k][j]);
	for(int i=1;i<=n;i++){
		if(f[i][x]+f[x][i]>max_&&f[i][x]<INF&&f[x][i]<INF)max_=f[i][x]+f[x][i];
	}
	cout<<max_;
	return 0;
}//求调