PAL2_6

package pal;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
 *
 * @author Alisa
 */
public class Main {

    static public int N; //hotels counts = |vertexes|
    static public int M; //track counts = |edges|
    static public int[][] edges;
    static public int indexConnection = 0;
    static public boolean notConn = false;
    static public int[][] vertexes;

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] in = br.readLine().split(" ");
        N = Integer.parseInt(in[0]);
        M = Integer.parseInt(in[1]);
        vertexes = new int[N][2]; //aktualni delka do vrcholu, delka posledni hrany vstoupivsi do vrcholu
        edges = new int[M][3]; //vrchol A, vrchol B, delka hrany AB
        int max = 0;
        for (int i = 0; i < M; i++) {
            in = br.readLine().split(" ");
            //x,y,z
            edges[i][0] = Integer.parseInt(in[0])-1; //x vertex
            edges[i][1] = Integer.parseInt(in[1])-1; //y vertex
            edges[i][2] = Integer.parseInt(in[2]); //distance between x and y
        }
        //sorted by distance
        edges = sortArrayByColumn(2);

        for (int i = 0; i < M; i++) {
            //predchozi hrana vrcholu A == soucasna hrana && predchozi hrana vrcholu B == soucasna hrana
            if (vertexes[edges[i][0]][1] == edges[i][2] && vertexes[edges[i][1]][1] == edges[i][2]) {   //delka do vrcholu A nebo B mensi jak nova hrana -> nahradime ji
                if (vertexes[edges[i][0]][0] < edges[i][2]) {
                    vertexes[edges[i][0]][0] = edges[i][2];
                    if (edges[i][2] > max) {
                        max = edges[i][2];
                    }
                }
                if (vertexes[edges[i][1]][0] < edges[i][2]) {
                    vertexes[edges[i][1]][0] = edges[i][2];
                    if (edges[i][2] > max) {
                        max = edges[i][2];
                    }
                }
                continue;
            }
            //predchozi hrana vrcholu A a B != soucasna hrana
            if (vertexes[edges[i][0]][1] != edges[i][2] && vertexes[edges[i][1]][1] != edges[i][2]) {
                int help = vertexes[edges[i][0]][0];
                //delka ve vrcholu A < nez B + nova cesta
                if (help < (vertexes[edges[i][1]][0] + edges[i][2])) {
                    vertexes[edges[i][0]][1] = edges[i][2];
                    vertexes[edges[i][0]][0] = vertexes[edges[i][1]][0] + edges[i][2];
                    if (vertexes[edges[i][0]][0] > max) {
                        max = vertexes[edges[i][0]][0];
                    }
                }
                //delka ve vrcholu B < nez A + nova cesta
                if (vertexes[edges[i][1]][0] < (help + edges[i][2])) {
                    vertexes[edges[i][1]][1] = edges[i][2];
                    vertexes[edges[i][1]][0] = help + edges[i][2];
                    if (vertexes[edges[i][1]][0] > max) {
                        max = vertexes[edges[i][1]][0];
                    }
                }
                continue;
            }
            //predchozi hrana vrcholu A == soucasna hrana
            if(vertexes[edges[i][0]][1] == edges[i][2])
            {
                int help = vertexes[edges[i][1]][0];
                if(help < edges[i][2])
                {   vertexes[edges[i][1]][1] = edges[i][2];
                    vertexes[edges[i][1]][0] = edges[i][2];
                    if (vertexes[edges[i][1]][0] > max) {
                        max = vertexes[edges[i][1]][0];
                    }
                }
                if(help + edges[i][2] > vertexes[edges[i][0]][0])
                {   vertexes[edges[i][0]][1] = edges[i][2];
                    vertexes[edges[i][0]][0] = help + edges[i][2];
                    if (vertexes[edges[i][0]][0] > max) {
                        max = vertexes[edges[i][0]][0];
                    }
                }
                continue;
            }
             //predchozi hrana vrcholu B == soucasna hrana
            if(vertexes[edges[i][1]][1] == edges[i][2])
            {
                int help = vertexes[edges[i][0]][0];
                if(help < edges[i][2])
                {   vertexes[edges[i][0]][1] = edges[i][2];
                    vertexes[edges[i][0]][0] = edges[i][2];
                    if (vertexes[edges[i][0]][0] > max) {
                        max = vertexes[edges[i][0]][0];
                    }
                }
                if(help + edges[i][2] > vertexes[edges[i][1]][0])
                {   vertexes[edges[i][1]][1] = edges[i][2];
                    vertexes[edges[i][1]][0] = help + edges[i][2];
                    if (vertexes[edges[i][1]][0] > max) {
                        max = vertexes[edges[i][1]][0];
                    }
                }
            }
        }
        System.out.println(max);
    }

    public static int[][] sortArrayByColumn(int column) {
        int[][] sortedArray = new int[M][3];
        int min = edges[0][column];
        int max = edges[0][column];
        //find min and max values for histogram from current column
        for (int i = 1; i < M; i++) {
            if (edges[i][column] < min) {
                min = edges[i][column];
            } else if (edges[i][column] > max) {
                max = edges[i][column];
            }
        }
        //histogram length from min to max
        int[] hist = new int[max - min + 1];
        for (int i = 0; i < M; i++) {
            hist[edges[i][column] - min]++;
        }
        //pole vyskytu
        hist[0]--;
        for (int i = 1; i < hist.length; i++) {
            hist[i] = hist[i] + hist[i - 1];
        }
        //min to max
        for (int i = M - 1; i >= 0; i--) {
            int histIndex = edges[i][column] - min;
            int index = hist[histIndex];
            sortedArray[index][column] = edges[i][column];
            sortedArray[index][1] = edges[i][1];
            sortedArray[index][0] = edges[i][0];
            hist[histIndex]--;
        }
        return sortedArray;
    }

}