from heapq import heappush, heappop
from sys import stdin
input = stdin.readline
inf = 1 << 60

def main():
    n, m = map(int, input().split())
    edges = [[] for _ in range(n)]
    for _ in range(m):
        u, v, c, d = map(int, input().split())
        edges[u-1].append([v-1, c, d])
        edges[v-1].append([u-1, c, d])
    for i in range(n):
        edges[i].sort(key=lambda x: x[0])

    # dijkstra
    dist = [inf] * n
    dist[0] = 0
    prev = [-1] * n
    heap = []
    heappush(heap, (0, 0))
    while heap:
        cost, u = heappop(heap)
        if u == n-1:
            break
        if dist[u] < cost:
            continue
        for v, c, d in edges[u]:
            if cost + c < dist[v]:
                dist[v] = cost + c
                prev[v] = u
                heappush(heap, (cost+c, v))
    dist1 = dist[n-1]

    def binary_search(u, v):
        left = 0
        right = len(edges[u]) - 1
        while left < right:
            center = (left + right) // 2
            if edges[u][center][0] < v:
                left = center + 1
            else:
                right = center
        edges[u][left][1], edges[u][left][2] = edges[u][left][2], edges[u][left][1]

    u = n-1
    while u > 0:
        v = prev[u]
        binary_search(u, v)
        binary_search(v, u)
        u = v

    # dijkstra
    dist = [inf] * n
    dist[0] = 0
    heap = []
    heappush(heap, (0, 0))
    while heap:
        cost, u = heappop(heap)
        if u == n-1:
            break
        if dist[u] < cost:
            continue
        for v, c, d in edges[u]:
            if cost + c < dist[v]:
                dist[v] = cost + c
                heappush(heap, (cost+c, v))

    print(dist1 + dist[n-1])

main()