#include <iostream>
#include <vector>
using namespace std;

int const infinity = 0x3F3F3F3F;

int main () {
    int n, m;
    cin >> n >> m;
    vector <vector <int> > a (n,
        vector <int> (n, infinity));
    for (int j = 0; j < m; j++) {
        int u, v, w;
        cin >> u >> v >> w;
        u -= 1;
        v -= 1;
        a[u][v] = w;
        a[v][u] = w;
    }

    for (int k = 0; k < n; k++)
        for (int i = 0; i < n; i++)
            for (int j = 0; j < n; j++)
                if (a[i][j] > a[i][k] + a[k][j])
                    a[i][j] = a[i][k] + a[k][j];

    int x = 0, y = n - 1;
    cout << a[x][y] << endl;
    return 0;
}