#include<iostream>

#include<cstdio>

#include<cstring>

#include<queue>

#include<algorithm>

#include<utility>

#include<vector>

#include<functional>

#include<ctype.h>

using namespace std;

typedef pair<int,int> pairr;

const int maxn=1005;

inline int read()

{

    int x=0,w=0;char c=getchar();

    while(!isdigit(c))w|=c=='-',c=getchar();

    while(isdigit(c))x=(x<<3)+(x<<1)+(c^48),c=getchar();

    return w?-x:x;

}

int mapp[maxn][maxn];

int n,m,t;

int dis[maxn];

inline void dijkstra(int st)

{

    memset(dis,0x3f3f3f3f,sizeof dis);

    priority_queue <pairr,vector<pairr >,greater<pairr > >q;

    q.push(make_pair(0,st));dis[st]=0;

    while(!q.empty())

    {

        int v=q.top().second;q.pop();

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

            if(mapp[v][i])

            {

                if(dis[i]>dis[v]+mapp[v][i])

                {

                    dis[i]=dis[v]+mapp[v][i];

                    q.push(make_pair(dis[i],i));

                }

            }

    }

}

int way[maxn];

int main()

{

    n=read();m=read();t=read();

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

        mapp[read()][read()]=read();

    dijkstra(t);

    for(int i=1;i<=n;i++)way[i]=dis[i];

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

        for(int j=1;j<i;j++)swap(mapp[i][j],mapp[j][i]);

    dijkstra(t);

    int ans=0;

    for(int i=1;i<=n;i++)ans=max(ans,dis[i]+way[i]);

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

    return 0;

}