#include <iostream>

#include <cstdio>

#include <cstring>

using namespace std;

#define INF 10000

const int maxn = ;

int r[maxn][maxn];

int main() {

    int n, m;

    while (cin>>n>>m)

     {

        memset (r, INF, sizeof(r));

        int x, y, v;

for (int i = ; i < m; i++)

         {

            cin>>x>>y>>v;

            if (r[x][uy] > v)

                r[x][y] = r[y][x] = v;

        }

for (int i = ; i < n ;i++)

            r[i][i] = ;

for (int k = ; k < n; k++)

            for (int i = ; i < n; i++)

                for (int j = ; j < n; j++)

                {

                    if (r[i][k] + r[k][j] < r[i][j])

                           r[i][j] = r[j][i] = r[i][k] + r[k][j];

                }

cin>>x>>y;

if (r[x][y] < INF)

            cout<<r[x][y]<<endl;

        else

            cout<<"-1"<<endl;

    }

    return ;

}