#include <bits/stdc++.h>
#pragma GCC optimize("O2")
using namespace std;
const int MAXN = 1e6 + 10;
const long long MOD = 1e9 + 7;
const long long MOD2 = 998244353;
const long long INF = 8e18;
const int LOG = 20;
long long pw(long long a, long long b, long long mod) {
  return (!b ? 1
             : (b & 1 ? (a * pw(a * a % mod, b / 2, mod)) % mod
                      : pw(a * a % mod, b / 2, mod)));
}
vector<pair<long long, long long> > G[MAXN];
vector<long long> top, adj[MAXN];
long long mark[MAXN], C[MAXN], cnt;
long long res[MAXN], dp[MAXN];
void DFS(int v) {
  mark[v] = 1;
  for (auto u : G[v]) {
    if (!mark[u.first]) DFS(u.first);
  }
  top.push_back(v);
}
void dfs(int v) {
  C[v] = cnt;
  for (auto u : adj[v]) {
    if (!C[u]) {
      dfs(u);
    }
  }
}
long long calc(long long x) {
  long long d = 0, up = 1e9;
  while (up - d > 1) {
    long long mid = (up + d) / 2;
    if (x >= (mid + 1) * mid / 2) {
      d = mid;
    } else {
      up = mid;
    }
  }
  return (d + 1) * x - ((d + 2) * (d + 1) * (d) / 6);
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    int a, b, c;
    cin >> a >> b >> c;
    G[a].push_back(make_pair(b, c));
    adj[b].push_back(a);
  }
  for (int i = 1; i <= n; i++) {
    if (!mark[i]) {
      DFS(i);
    }
  }
  for (int i = n - 1; ~i; i--) {
    if (!C[top[i]]) {
      cnt++;
      dfs(top[i]);
    }
  }
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    for (auto u : G[i]) {
      if (C[u.first] == C[i]) {
        res[C[i]] += calc(u.second);
      }
    }
  }
  for (int i = 1; i <= n; i++) {
    dp[i] = res[i];
  }
  for (auto v : top) {
    for (auto u : G[v]) {
      if (C[u.first] == C[v]) continue;
      dp[C[v]] = max(dp[C[v]], dp[C[u.first]] + res[C[v]] + u.second);
    }
  }
  int node;
  cin >> node;
  cout << dp[C[node]] << "\n";
  return 0;
}
