import java.io.*;
import java.util.*;


public class Main_yukicoder845 {

	private static Scanner sc;
	private static Printer pr;

	private static void solve() {
		int n = sc.nextInt();
		int m = sc.nextInt();

		FloydWarshall fw = new FloydWarshall(n);
		for (int i = 0; i < m; i++) {
			int a = sc.nextInt() - 1;
			int b = sc.nextInt() - 1;
			int c = sc.nextInt();
			
			if (fw.d[a][b] == fw.INF || c > fw.d[a][b]) {
				fw.addEdge(a, b, c);
				fw.addEdge(b, a, c);
			}
		}
		
		long max = 0;
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				long tmp = fw.getShortestPath(i, j);
				if (i != j && tmp != fw.INF) {
					max = Math.max(max, tmp);
				}
			}
		}
		
		pr.println(max);
	}

	// 全点対最短路 FloydWarshall O(V^3)
	private static class FloydWarshall {
		long[][] d;
		int n;
		long[][] result;
		boolean nf; // NEGATIVE CYCLE flag

		final long INF = Long.MAX_VALUE;

		FloydWarshall(int n) {
			this.n = n;
			d = new long[n][n];
			for (int i = 0; i < n; i++) {
				Arrays.fill(d[i], INF);
				d[i][i] = 0;
			}
			nf = false;
		}

		// i, j:0-indexed
		public void addEdge(int i, int j, int c) {
			d[i][j] = c;
		}

		// 負閉路があるときは-INFを返す
		public long getShortestPath(int i, int j) {
			if (nf) {
				return -INF;
			}

			if (result == null) {
				for (int kk = 0; kk < n; kk++) {
					for (int ii = 0; ii < n; ii++) {
						for (int jj = 0; jj < n; jj++) {
//							d[ii][jj] = Math.min(d[ii][jj], d[ii][kk] + d[kk][jj]);
							if (d[ii][kk] != INF && d[kk][jj] != INF && d[ii][jj] > d[ii][kk] + d[kk][jj]) {
								d[ii][jj] = d[ii][kk] + d[kk][jj];
							}
						}
					}
				}

				for (int k = 0; k < n; k++) {
					if (d[k][k] < 0) {
						nf = true;
						return -INF;
					}
				}

				result = d;
			}

			return result[i][j];
		}
	}

	// ---------------------------------------------------
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pr = new Printer(System.out);
			
		solve();
			
		pr.close();
		sc.close();
	}

	static class Printer extends PrintWriter {
		Printer(OutputStream out) {
			super(out);
		}
	}
}