#include <bits/stdc++.h>
using namespace std;
int n, m, tot;
vector<pair<int, int> > g[1000005], rg[1000005], ng[1000005];
vector<int> vs;
bool u[1000005];
int cmp[1000005];
long long wt[1000005];
long long dp[1000005];
int pre[20005];
long long pp[20005];
long long calc(int x) {
  int pos = lower_bound(pre, pre + 20001, x) - pre;
  return (long long)x * (pos + 1) - pp[pos] + (pre[pos] - x);
}
void ndfs(int x) {
  u[x] = 1;
  for (pair<int, int> &y : g[x])
    if (!u[y.first]) ndfs(y.first);
  vs.push_back(x);
}
void rdfs(int x, int k) {
  u[x] = 1;
  cmp[x] = k;
  for (pair<int, int> &y : rg[x])
    if (!u[y.first]) rdfs(y.first, k);
}
long long dfs(int x) {
  long long &res = dp[x];
  if (res) return res;
  for (pair<int, int> &y : ng[x]) {
    res = max(res, dfs(y.first) + y.second);
  }
  return res += wt[x];
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  for (int i = 1; i <= 20000; i++) {
    pre[i] = pre[i - 1] + i;
    pp[i] = pp[i - 1] + pre[i];
  }
  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));
    rg[b].push_back(make_pair(a, c));
  }
  for (int i = 1; i <= n; i++)
    if (!u[i]) ndfs(i);
  memset(u, 0, sizeof(u));
  for (int i = n - 1; i >= 0; i--)
    if (!u[vs[i]]) rdfs(vs[i], ++tot);
  for (int x = 1; x <= n; x++) {
    for (pair<int, int> &y : g[x]) {
      if (cmp[x] == cmp[y.first])
        wt[cmp[x]] += calc(y.second);
      else
        ng[cmp[x]].push_back(make_pair(cmp[y.first], y.second));
    }
  }
  int src;
  cin >> src;
  cout << dfs(cmp[src]) << endl;
  return 0;
}
