# 택배 배송

import sys
import heapq as h

input = sys.stdin.readline

def solution():
    n, m = map(int, input().rstrip().split())

    g = {i+1: [] for i in range(n)}
    dk = [float('inf') for _ in range(n+1)]

    for _ in range(m):
        v, w, k = map(int, input().rstrip().split())
        g[v].append((k, w))
        g[w].append((k, v))
    
    heap = []
    h.heappush(heap, (0, 1))
    dk[1] = 0
    while heap:
        now_dist, now_v = h.heappop(heap)

        if now_dist > dk[now_v]:
            continue

        for nxt_k, nxt_v in g[now_v]:
            new_dist = dk[now_v]+nxt_k
            if new_dist < dk[nxt_v]:
                dk[nxt_v] = min(dk[nxt_v], dk[now_v]+nxt_k)
                h.heappush(heap, (new_dist, nxt_v))

    print(dk[n])

    return


solution()

"""
걸린 시간: 11:10~

시간 복잡도: 

해설: 다익스트라
"""