#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <climits>#include <string>#include <iostream>#include <map>#include <cstdlib>#include <list>#include <set>#include <queue>#include <stack>using namespace std;typedef long long LL;const int maxn = 1000 + 5;const int INF = INT_MAX / 2;const int maxm = 100000 + 5;int first[maxn],nxt[maxm],u[maxm],v[maxm],w[maxm];int N,M,X,d1[maxn],d2[maxn];bool vis[maxn];void spfa(int *v,int *d) {    memset(vis,0,sizeof(vis));    for(int i = 1;i <= N;i++) d[i] = INF;    d[X] = 0;    queue<int> q;    q.push(X);    while(!q.empty()) {        int u = q.front(); q.pop();        vis[u] = false;        for(int i = first[u];i != 0;i = nxt[i]) {            if(d[v[i]] > d[u] + w[i]) {                d[v[i]] = d[u] + w[i];                if(!vis[v[i]]) {                    vis[v[i]] = true;                    q.push(v[i]);                }            }        }    }}void adde(int u,int i) {    nxt[i] = first[u];    first[u] = i;}int main() {    while(scanf("%d%d%d",&N,&M,&X) != EOF) {        memset(first,0,sizeof(first));        memset(nxt,0,sizeof(nxt));        for(int i = 1;i <= M;i++) {            scanf("%d%d%d",&u[i],&v[i],&w[i]);            adde(u[i],i);        }        spfa(v,d1);        memset(first,0,sizeof(first));        memset(nxt,0,sizeof(nxt));        for(int i = 1;i <= M;i++) {            adde(v[i],i);        }        spfa(u,d2);        int ans = 0;        for(int i = 1;i <= N;i++) ans = max(ans,d1[i] + d2[i]);        printf("%d\n",ans);    }    return 0;}