#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
struct Edge {
  long long int from, to, cap, flow, index;
  Edge(long long int from, long long int to, long long int cap,
       long long int flow, long long int index)
      : from(from), to(to), cap(cap), flow(flow), index(index) {}
};
struct PushRelabel {
  long long int N;
  vector<vector<Edge>> G;
  vector<long long> excess;
  vector<long long int> dist, active, count;
  queue<long long int> Q;
  PushRelabel(long long int N)
      : N(N), G(N), excess(N), dist(N), active(N), count(2 * N) {}
  void AddEdge(long long int from, long long int to, long long int cap) {
    G[from].push_back(Edge(from, to, cap, 0, G[to].size()));
    if (from == to) G[from].back().index++;
    G[to].push_back(Edge(to, from, 0, 0, G[from].size() - 1));
  }
  void Enqueue(long long int v) {
    if (!active[v] && excess[v] > 0) {
      active[v] = true;
      Q.push(v);
    }
  }
  void Push(Edge &e) {
    long long int amt = min(excess[e.from], e.cap - e.flow);
    if (dist[e.from] <= dist[e.to] || amt == 0) return;
    e.flow += amt;
    G[e.to][e.index].flow -= amt;
    excess[e.to] += amt;
    excess[e.from] -= amt;
    Enqueue(e.to);
  }
  void Gap(long long int k) {
    for (long long int v = 0; v < N; v++) {
      if (dist[v] < k) continue;
      count[dist[v]]--;
      dist[v] = max(dist[v], N + 1);
      count[dist[v]]++;
      Enqueue(v);
    }
  }
  void Relabel(long long int v) {
    count[dist[v]]--;
    dist[v] = 2 * N;
    for (long long int i = 0; i < G[v].size(); i++)
      if (G[v][i].cap - G[v][i].flow > 0)
        dist[v] = min(dist[v], dist[G[v][i].to] + 1);
    count[dist[v]]++;
    Enqueue(v);
  }
  void Discharge(long long int v) {
    for (long long int i = 0; excess[v] > 0 && i < G[v].size(); i++)
      Push(G[v][i]);
    if (excess[v] > 0) {
      if (count[dist[v]] == 1)
        Gap(dist[v]);
      else
        Relabel(v);
    }
  }
  long long GetMaxFlow(long long int s, long long int t) {
    count[0] = N - 1;
    count[N] = 1;
    dist[s] = N;
    active[s] = active[t] = true;
    for (long long int i = 0; i < G[s].size(); i++) {
      excess[s] += G[s][i].cap;
      Push(G[s][i]);
    }
    while (!Q.empty()) {
      long long int v = Q.front();
      Q.pop();
      active[v] = false;
      Discharge(v);
    }
    long long totflow = 0;
    for (long long int i = 0; i < G[s].size(); i++) totflow += G[s][i].flow;
    return totflow;
  }
};
void solve() {
  long long int n;
  cin >> n;
  long long int m;
  cin >> m;
  long long int x;
  cin >> x;
  vector<array<long long int, 3>> edge(m);
  for (long long int i = 0; i < m; i++) {
    cin >> edge[i][0];
    edge[i][0]--;
    cin >> edge[i][1];
    edge[i][1]--;
    cin >> edge[i][2];
  }
  long double low = 0;
  long double high = 1e9;
  for (long long int i = 0; i < 100; i++) {
    long double mid = (low + high) / (long double)2;
    PushRelabel G(n);
    for (auto e : edge) {
      G.AddEdge(e[0], e[1], (long long int)(e[2] / mid));
    }
    if (G.GetMaxFlow(0, n - 1) >= x) {
      low = mid;
    } else {
      high = mid;
    }
  }
  long double avg = (low + high) / (long double)2;
  cout << fixed << setprecision(9) << (long double)x * avg << '\n';
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  solve();
  cerr << "Time : "
       << 1000 * ((long double)clock()) / (long double)CLOCKS_PER_SEC << "ms\n";
  return 0;
}
