#include <bits/stdc++.h>   using namespace std;   template <typename T>   T BigMod(T b, T p, T m) {     if (p == 0) return 1;     if (p % 2 == 0) {       T s = BigMod(b, p / 2, m);       return ((s % m) * (s % m)) % m;     }     return ((b % m) * (BigMod(b, p - 1, m) % m)) % m;   }   template <typename T>   T ModInv(T b, T m) {     return BigMod(b, m - 2, m);   }   template <typename T>   T in() {     char ch;     T n = 0;     bool ng = false;     while (1) {       ch = getchar();       if (ch ==  - ) {         ng = true;         ch = getchar();         break;       }       if (ch >=  0  && ch <=  9 ) break;     }     while (1) {       n = n * 10 + (ch -  0 );       ch = getchar();       if (ch <  0  || ch >  9 ) break;     }     return (ng ? -n : n);   }   template <typename T>   T POW(T B, T printf) {     if (printf == 0) return 1;     if (printf & 1)       return B * POW(B, printf - 1);     else       return (POW(B, printf / 2) * POW(B, printf / 2));   }   template <typename T>   T Bigmod(T b, T p, T m) {     if (p == 0)       return 1;     else if (!(p & 1))       return (Bigmod(b, p / 2, m) * Bigmod(b, p / 2, m)) % m;     else       return ((b % m) * Bigmod(b, p - 1, m)) % m;   }   template <typename T>   T Dis(T x1, T y1, T x2, T y2) {     return sqrt((x1 - x2 * x1 - x2) + (y1 - y2 * y1 - y2));   }   template <typename T>   T Angle(T x1, T y1, T x2, T y2) {     return atan(double(y1 - y2) / double(x1 - x2));   }   template <typename T>   T DIFF(T a, T b) {     T d = a - b;     if (d < 0)       return -d;     else       return d;   }   template <typename T>   T ABS(T a) {     if (a < 0)       return -a;     else       return a;   }   template <typename T>   T gcd(T a, T b) {     if (a < 0) return gcd(-a, b);     if (b < 0) return gcd(a, -b);     return (b == 0) ? a : gcd(b, a % b);   }   template <typename T>   T lcm(T a, T b) {     if (a < 0) return lcm(-a, b);     if (b < 0) return lcm(a, -b);     return a * (b / gcd(a, b));   }   template <typename T>   T euclide(T a, T b, T &x, T &y) {     if (a < 0) {       T d = euclide(-a, b, x, y);       x = -x;       return d;     }     if (b < 0) {       T d = euclide(a, -b, x, y);       y = -y;       return d;     }     if (b == 0) {       x = 1;       y = 0;       return a;     } else {       T d = euclide(b, a % b, x, y);       T t = x;       x = y;       y = t - (a / b) * y;       return d;     }   }   template <typename T>   void ia(T a[], int n) {     for (int i = 0; i < n; i++) cin >> a[i];   }   template <typename T>   void pa(T a[], int n) {     for (int i = 0; i < n - 1; i++) cout << a[i] <<    ;     cout << a[n - 1] << endl;   }   template <typename T>   long long int isLeft(T a, T b, T c) {     return (a.x - b.x) * (b.y - c.y) - (b.x - c.x) * (a.y - b.y);   }   int Set(int N, int pos) { return N = N | (1 << pos); }   int Reset(int N, int pos) { return N = N & ~(1 << pos); }   bool Check(int N, int pos) { return (bool)(N & (1 << pos)); }   template <class T, class first>   inline T togglebit(T a, first i) {     T t = 1;     return (a ^ (t << i));   }   int toInt(string s) {     int sm;     stringstream ss(s);     ss >> sm;     return sm;   }   int toLlint(string s) {     long long int sm;     stringstream ss(s);     ss >> sm;     return sm;   }   int cdigittoint(char ch) { return ch -  0 ; }   bool isVowel(char ch) {     ch = toupper(ch);     if (ch ==  A  || ch ==  U  || ch ==  I  || ch ==  O  || ch ==  E )       return true;     return false;   }   bool isConst(char ch) {     if (isalpha(ch) && !isVowel(ch)) return true;     return false;   }   double DEG(double x) { return (180.0 * x) / (2.0 * acos(0.0)); }   double RAD(double x) { return (x * (double)2.0 * acos(0.0)) / (180.0); }   vector<int> adj[200007], dag[200007], par[200007];   int DP[200007][18], siz[200007];   long long int dis[200007];   int L[200007];   int inDeg[200007];   bool vis[200007];   void Init(int n) {     for (int i = 0; i <= n; i++) {       dis[i] = 1LL << 60;       adj[i].clear();       dag[i].clear();       par[i].clear();       inDeg[i] = siz[i] = vis[i] = 0;       for (int j = 0; j < 18; j++) DP[i][j] = -1;     }   }   void Update(int u, int p) {     DP[u][0] = p;     L[u] = L[p] + 1;     adj[p].push_back(u);     for (int i = 1; i < 18; i++)       if (DP[u][i - 1] != -1) DP[u][i] = DP[DP[u][i - 1]][i - 1];   }   int LCA(int p, int q) {     if (L[p] < L[q]) swap(p, q);     for (int i = 18 - 1; i >= 0; i--)       if (L[p] - (1 << i) >= L[q]) p = DP[p][i];     if (p == q) return p;     for (int i = 18 - 1; i >= 0; i--)       if (DP[p][i] != -1 && DP[p][i] != DP[q][i]) {         p = DP[p][i];         q = DP[q][i];       }     return DP[p][0];   }   void Dijkstra(int n, int s) {     set<pair<long long int, long long int> > pq;     pq.insert(make_pair(0, s));     dis[s] = 0;     L[s] = 1;     while (!pq.empty()) {       pair<long long int, long long int> tmp = *pq.begin();       pq.erase(pq.begin());       int u = tmp.second;       for (int i = 0; i < adj[u].size(); i += 2) {         int v = adj[u][i];         int w = adj[u][i + 1];         if (dis[v] > dis[u] + w) {           dis[v] = dis[u] + w;           pq.insert(make_pair(dis[v], v));         }       }     }     for (int i = 1; i <= n; i++) {       for (int j = 0; j < adj[i].size(); j += 2) {         int v = adj[i][j];         int w = adj[i][j + 1];         if (dis[i] + w == dis[v]) {           inDeg[v]++;           dag[i].push_back(v);           par[v].push_back(i);         }       }       adj[i].clear();     }   }   void TopSort(int s) {     queue<int> q;     q.push(s);     L[s] = 1;     while (!q.empty()) {       int u = q.front();       q.pop();       if (!par[u].empty()) {         int lca = par[u][0];         for (int i = 1; i < par[u].size(); i++) {           lca = LCA(lca, par[u][i]);         }         Update(u, lca);       }       for (int i = 0; i < dag[u].size(); i++) {         int v = dag[u][i];         inDeg[v]--;         if (!inDeg[v]) q.push(v);       }     }   }   void Dfs(int u) {     siz[u] = 1;     vis[u] = 1;     for (int i = 0; i < adj[u].size(); i++) {       Dfs(adj[u][i]);       siz[u] += siz[adj[u][i]];     }   }   int main() {     int n, m, s;     scanf( %d%d%d , &n, &m, &s);     Init(n);     for (int i = 1; i <= m; i++) {       int u, v, w;       scanf( %d%d%d , &u, &v, &w);       adj[u].push_back(v);       adj[u].push_back(w);       adj[v].push_back(u);       adj[v].push_back(w);     }     Dijkstra(n, s);     TopSort(s);     Dfs(s);     int mx = 0;     for (int i = 1; i <= n; i++) {       if (i != s) mx = max(mx, siz[i]);     }     cout << mx << endl;     return 0;   }