#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;

#define scan(x) do{while((x=getchar())<'0'); for(x-='0'; '0'<=(_=getchar()); x=(x<<3)+(x<<1)+_-'0');}while(0)
char _;
#define complete_unique(a) a.erase(unique(a.begin(),a.end()),a.end())
#define all(a) a.begin(),a.end()
#define println printf("\n");
#define readln(x) getline(cin,x);
#define pb push_back
#define endl "\n"
#define INT_INF 0x3f3f3f3f
#define LL_INF 0x3f3f3f3f3f3f3f3f
#define MOD 1000000007
#define MOD2 1190492669
#define SEED 131
#define mp make_pair
#define fastio cin.tie(0); cin.sync_with_stdio(0);

#define MAXN 1005

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef unordered_map<int,int> umii;
typedef pair<int,int> pii;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef pair<int,pii> triple;
typedef int8_t byte;

mt19937 g1(time(0));

int randint(int a, int b){return uniform_int_distribution<int>(a, b)(g1);}
ll randlong(ll a,ll b){return uniform_int_distribution<long long>(a, b)(g1);}

ll gcd(ll a, ll b){return b == 0 ? a : gcd(b, a % b);}
ll lcm(ll a, ll b){return a*b/gcd(a,b);}
ll fpow(ll  b, ll exp, ll mod){if(exp == 0) return 1;ll t = fpow(b,exp/2,mod);if(exp&1) return t*t%mod*b%mod;return t*t%mod;}
ll divmod(ll i, ll j, ll mod){i%=mod,j%=mod;return i*fpow(j,mod-2,mod)%mod;}

int num_nodes,num_edges,T,dis[2][MAXN],res;
vector<pii> gg[MAXN],rev[MAXN];

inline void init(int node, int s, vector<pii> (&connections)[MAXN]){
    memset(dis[s],0x3f,sizeof dis[s]);
    queue<pii> q;
    q.push(mp(0,node));
    dis[s][node] = 0;
    while(q.size()){
        int d = q.front().first, node = q.front().second; q.pop();
        if(dis[s][node] < d) continue;
        for(pii check:connections[node]){
            if(dis[s][check.first] > dis[s][node]+check.second){
                dis[s][check.first] = dis[s][node]+check.second;
                q.push(mp(dis[s][check.first],check.first));
            }
        }
    }
}

int main(){
    scanf("%d %d %d",&num_nodes,&num_edges,&T);
    for(int i=1; i<=num_edges; i++){
        int a,b,w; scanf(" %d %d %d",&a,&b,&w);
        gg[a].pb(mp(b,w));
        rev[b].pb(mp(a,w));
    }
    init(T,0,gg);
    init(T,1,rev);
    for(int i=1; i<=num_nodes; i++)
        res = max(res,dis[0][i]+dis[1][i]);
    printf("%d\n",res);
}