#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 2;
vector<int> g[MAXN];
int d[MAXN], low[MAXN], scc[MAXN];
bool stacked[MAXN];
stack<int> s;
int ticks, current_scc;
void tarjan(int u) {
  d[u] = low[u] = ticks++;
  s.push(u);
  stacked[u] = true;
  const vector<int> &out = g[u];
  for (int k = 0, m = out.size(); k < m; ++k) {
    const int &v = out[k];
    if (d[v] == -1) {
      tarjan(v);
      low[u] = min(low[u], low[v]);
    } else if (stacked[v]) {
      low[u] = min(low[u], low[v]);
    }
  }
  if (d[u] == low[u]) {
    int v;
    do {
      v = s.top();
      s.pop();
      stacked[v] = false;
      scc[v] = current_scc;
    } while (u != v);
    current_scc++;
  }
}
vector<pair<long long, long long> > adj[2 * MAXN];
vector<pair<long long, pair<long long, long long> > > reg;
long long peso[2 * MAXN];
long long dp[2 * MAXN];
long long getval(long long x) {
  long long r = sqrt(2 * x);
  if (r * r + r > 2 * x) r--;
  return (r + 1) * x - (r * (r + 1) * (r + 2) / 6);
}
long long solve(long long u) {
  long long high = 0;
  if (dp[u] != -1) return dp[u];
  for (auto d : adj[u]) {
    long long v = d.first, w = d.second;
    high = max(high, solve(v) + w);
  }
  return dp[u] = high;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  ;
  memset(d, -1, sizeof(d));
  memset(scc, -1, sizeof(scc));
  long long n, m;
  cin >> n >> m;
  for (long long(i) = (0); (i) < (m); (i)++) {
    long long u, v, w;
    cin >> u >> v >> w;
    g[u].push_back(v);
    reg.push_back(make_pair((u), make_pair((v), (w))));
  }
  long long x;
  cin >> x;
  tarjan(x);
  long long tot = current_scc;
  for (auto t : reg) {
    long long u = t.first, v = t.second.first, w = t.second.second;
    if (scc[u] != -1 && scc[u] == scc[v]) {
      peso[scc[u]] += getval(w);
    } else if (scc[u] == -1 || scc[v] == -1)
      continue;
    else if (scc[u] != scc[v]) {
      adj[scc[u] + tot].push_back(make_pair(scc[v], w));
    }
  }
  for (long long(i) = (0); (i) < (tot); (i)++) {
    adj[i].push_back(make_pair(i + tot, peso[i]));
  }
  memset(dp, -1, sizeof(dp));
  cout << solve(scc[x]) << endl;
  return 0;
}
