#include<bits/stdc++.h>
#include<iostream>
#include<vector>
#include<cstring>
#include<algorithm>
#define maxn 205
using namespace std;
vector<pair<int, int> >E[maxn];
int n, m;
int d[maxn], inq[maxn];
void init(){
	for(int i = 0; i < maxn; i++) E[i].clear();
	for(int i = 0; i < maxn; i++) inq[i] = 0;
	for(int i = 0; i < maxn; i++) d[i] = 1e7;
}
int main(){
	while(cin >> n >> m){
		init();
        /*for(int i = 0; i < n; i++){
            printf("inq[%d] = %d \n", i, inq[i]);
        }
        for(int i = 0; i < n; i++){
           printf("d[%d] = %d \n", i, d[i]);
        }*/ //列印初始化
		for(int i = 0; i < m; i++){
			int x, y, z;scanf("%d%d%d", &x, &y, &z);
			E[x].push_back(make_pair(y, z));
			E[y].push_back(make_pair(x, z));//雙向表
		}
		/*for(int x = 0; x < m; x++){
            for(int i = 0; i < E[x].size(); i++)
            printf("E[%d][%d] = %d %d\n", x, i, E[x][i].first, E[x][i].second);
        }*/ //每個點都有邊的話可以這樣輸出
		int s, t;
		scanf("%d%d", &s, &t);
		queue<int> Q;
		Q.push(s), d[s] = 0; inq[s] = 1;
		while(!Q.empty()){
			int now = Q.front();
			Q.pop(), inq[now] = 0;
			for(int i = 0; i < E[now].size(); i++){
				int v = E[now][i].first;
				if(d[v] > d[now] + E[now][i].second){
					d[v] = d[now] +  E[now][i].second;
					if(inq[v] == 1) continue;
					inq[v] = 1;
					Q.push(v);
				}
			}
		}
		if(d[t] == 1e7){
            printf("-1\n");
		}else{
            printf("%d\n", d[t]);
		}
	}
	return 0;
}