#include <bits/stdc++.h>
using namespace std;
const int N = 1000010;
vector<long long> is_prime(N + 1, true);
long long to_int(string s) {
  stringstream geek(s);
  long long x = 0;
  geek >> x;
  return x;
}
string to_string(long long n) {
  ostringstream str1;
  str1 << n;
  string geek = str1.str();
  return geek;
}
bool sortinrev(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.first > b.first);
}
bool sortbysecdesc(const pair<int, int> &a, const pair<int, int> &b) {
  return a.second > b.second;
}
bool sortbysec(const pair<int, int> &a, const pair<int, int> &b) {
  return (a.second < b.second);
}
long long powerm(long long a, long long k) {
  if (!k) {
    return 1;
  }
  long long b = powerm(a, k / 2);
  b = b * b % (1000000000 + 7);
  if (k % 2) {
    return a * b % (1000000000 + 7);
  } else {
    return b;
  }
}
long long power(long long a, long long b) {
  if (b == 1) return a;
  if (b == 0) return 1;
  long long m1 = power(a, b / 2);
  if (b % 2) return m1 * m1 * a;
  return m1 * m1;
}
void seive_of_eras(long long n) {
  is_prime[0] = 0;
  is_prime[1] = 0;
  for (long long i = 2; i * i <= n; i++) {
    if (is_prime[i]) {
      for (long long j = i * i; j <= n; j += i) {
        is_prime[j] = false;
      }
    }
  }
}
bool isprime(long long a) {
  if (a <= 1) return false;
  if (a == 2 | a == 3) return true;
  if (a % 2 == 0 || a % 3 == 0) return false;
  for (long long i = 5; i * i <= a; i = i + 6) {
    if (a % i == 0 || a % (i + 2) == 0) return false;
  }
  return true;
}
struct Triple {
  long long x, y, z;
};
vector<long long> adj[N];
long long visited[N];
long long outgoing[N];
long long incoming[N];
long long diameter[N];
long long t_h[N], w_t[N];
vector<Triple> v;
void dfs(long long u, long long j, long long d) {
  visited[u] = 1;
  for (long long i = 0; i < adj[u].size(); i++) {
    if (visited[adj[u][i]] == 0) {
      if (diameter[adj[u][i]] != 0) d = min(d, diameter[adj[u][i]]);
      if (w_t[adj[u][i]]) {
        v.push_back({j, adj[u][i], d});
      }
      dfs(adj[u][i], j, d);
    }
  }
}
void codeit() {
  long long n, p;
  cin >> n >> p;
  for (long long i = 0; i < p; i++) {
    long long u, v, d;
    cin >> u >> v >> d;
    adj[u].push_back(v);
    adj[v].push_back(u);
    outgoing[u] = 1;
    incoming[v] = 1;
    diameter[u] = d;
  }
  for (long long i = 1; i <= n; i++) {
    if (outgoing[i] == 1 && incoming[i] == 0) {
      t_h[i] = 1;
    } else if (outgoing[i] == 0 && incoming[i] == 1) {
      w_t[i] = 1;
    }
  }
  for (long long i = 1; i <= n; i++) {
    if (t_h[i] == 1) {
      dfs(i, i, diameter[i]);
    }
  }
  cout << v.size() << endl;
  for (long long i = 0; i < v.size(); i++) {
    cout << v[i].x << " " << v[i].y << " " << v[i].z << endl;
  }
  return;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(0);
  long long tt;
  tt = 1;
  for (long long i = 0; i < tt; i++) {
    codeit();
  }
}
