#include <cstring>
#include <fstream>
#include <algorithm>
#include <vector>

using namespace std;

inline bool compare(const pair<int, int>& P1, const pair<int, int>& P2)
{
    return P1.second < P2.second;
}

int N, M, X, Y, K, Kmax;
vector<pair<int, int> > V[250002];
int testnow;

int main()
{
    ifstream fin("pscnv.in");
    ofstream fout("pscnv.out");

    fin >> N >> M >> X >> Y;
    for (int i = 1, nod1, nod2, cost; i <= M; ++i)
    {
        fin >> nod1 >> nod2 >> cost;
        V[nod1].push_back(make_pair(nod2, cost));
        Kmax = max(Kmax, cost);
    }

    for (int i = 1; i <= N; ++i)
        sort(V[i].begin(), V[i].end(), compare);

    fout << K;

    fin.close();
    fout.close();
}