#include <bits/stdc++.h>
using namespace std;
const int M = 1000005;
const int up = 20000;
long long read() {
  long long x = 0, f = 1;
  char c;
  while ((c = getchar()) < '0' || c > '9') {
    if (c == '-') f = -1;
  }
  while (c >= '0' && c <= '9') {
    x = (x << 3) + (x << 1) + (c ^ 48);
    c = getchar();
  }
  return x * f;
}
long long n, m, k, tot, f[M], p[M], a[M], dp[M];
long long Index, cnt, col[M], low[M], dfn[M], in[M];
stack<long long> s;
vector<pair<long long, long long> > g[M];
struct edge {
  long long v, c, next;
} e[2 * M];
void dfs(long long u) {
  low[u] = dfn[u] = ++Index;
  s.push(u);
  in[u] = 1;
  for (long long i = f[u]; i; i = e[i].next) {
    long long v = e[i].v;
    if (!dfn[v]) {
      dfs(v);
      low[u] = min(low[u], low[v]);
    } else if (in[v])
      low[u] = min(low[u], dfn[v]);
  }
  if (low[u] == dfn[u]) {
    long long v = 0;
    cnt++;
    do {
      v = s.top();
      s.pop();
      col[v] = cnt;
      in[v] = 0;
    } while (u ^ v);
  }
}
void work(long long u) {
  for (long long i = 0; i < g[u].size(); i++) {
    long long v = g[u][i].first, c = g[u][i].second;
    if (!dp[v]) work(v);
    dp[u] = max(dp[u], dp[v] + c);
  }
  dp[u] += a[u];
}
long long cal(long long x) {
  long long t = 0, l = 1, r = up;
  while (l <= r) {
    long long mid = (l + r) >> 1;
    if (mid * (mid + 1) / 2 <= x) {
      t = mid;
      l = mid + 1;
    } else
      r = mid - 1;
  }
  return x * (t + 1) - p[t];
}
signed main() {
  n = read();
  m = read();
  for (long long i = 1; i <= m; i++) {
    long long u = read(), v = read(), c = read();
    e[++tot] = edge{v, c, f[u]}, f[u] = tot;
  }
  k = read();
  for (long long i = 1; i <= up; i++) p[i] = p[i - 1] + (i + 1) * i / 2;
  dfs(k);
  for (long long i = 1; i <= n; i++)
    for (long long j = f[i]; j; j = e[j].next) {
      long long u = col[i], v = col[e[j].v];
      if (u ^ v)
        g[u].push_back(make_pair(v, e[j].c));
      else
        a[u] += cal(e[j].c);
    }
  work(col[k]);
  printf("%lld\n", dp[col[k]]);
}
