//목적지 직행 , 현재까지 거리 + 현재에서 목적지 거리
            if(distance[destination.index] > distance[current.index] + destination.distance) {
                // 최소 거리 비용 갱신
                distance[destination.index] = distance[current.index] + destination.distance;
                priorityQueue.add(new Node(destination.index, distance[destination.index]));
            }

package problem.shortest.Q1916;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.PriorityQueue;

public class Main_1916 {
    static final int INF = 987654321;
    static int V, E, start,end;
    static List<List<Node>> adList;
    static int[] distance;
    static boolean[] visited;
    static PriorityQueue<Node> priorityQueue;


    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        V = Integer.parseInt(br.readLine());
        E = Integer.parseInt(br.readLine());

        adList = new ArrayList<>();
        // 인덱스를 1부터 하기 위해서 한 개를 넣어둠
        adList.add(new <Node>ArrayList());
        for (int i = 1; i <= V; i++) {
            adList.add(new <Node>ArrayList());
        }

        for (int i = 0; i < E; i++) {
            String[] temp = br.readLine().split(" ");
            int u = Integer.parseInt(temp[0]);
            int v = Integer.parseInt(temp[1]);
            int cost = Integer.parseInt(temp[2]);
            adList.get(u).add(new Node(v, cost));
        }
        String temp[] = br.readLine().split(" ");
        start = Integer.parseInt(temp[0]);
        end = Integer.parseInt(temp[1]);

        solve(start);


        if (distance[end] == INF) {
            System.out.println("INF");
        } else {
            System.out.println(distance[end]);
        }

    }

    private static void solve(int start) {
        priorityQueue = new PriorityQueue<>();
        visited = new boolean[V +1];

        distance = new int[V + 1];
        Arrays.fill(distance, INF);

        distance[start] = 0;
        priorityQueue.add(new Node(start, 0));

        while(!priorityQueue.isEmpty()) {
            Node current =  priorityQueue.poll();

            if(visited[current.index]){
                continue;
            }
            visited[current.index] = true;
            // 연결된 정점들을 확인
            for(Node destination : adList.get(current.index)) {
                //목적지 직행 , 현재까지 거리 + 현재에서 목적지 거리
                if(distance[destination.index] > distance[current.index] + destination.distance) {
                    // 최소 거리 비용 갱신
                    distance[destination.index] = distance[current.index] + destination.distance;
                    priorityQueue.add(new Node(destination.index, distance[destination.index]));
                }
            }
        }
    }
}

class Node implements Comparable<Node>{
    int index;
    int distance;

    public Node(int index, int distance) {
        this.index = index;
        this.distance = distance;
    }

    @Override
    public int compareTo(Node target) {
        // 작은 거리 비용이 먼저 오도록
        return this.distance - target.distance;
    }
}