import sys
from heapq import * 

input = sys.stdin.readline

INF = 10 ** 15

N, M = map(int, input().split())
adj = [dict() for _ in range(N)]
uv2d = dict()
for _ in range(M):
    u, v, c, d = map(int, input().split())
    u -= 1
    v -= 1
    adj[u][v] = adj[v][u] = c
    uv2d[(u, v)] = uv2d[(v, u)] = d

# pq が持つのは、(コスト * N) + 頂点
# dijkstra 1回目
pq = [0]
dp = [INF] * N
dp[0] = 0
parent = [-1] * N
while pq:
    cost, v = divmod(heappop(pq), N)
    if cost > dp[v]:
        continue
    for nv, dist in adj[v].items():
        if dp[nv] > dp[v] + dist:
            dp[nv] = dp[v] + dist
            parent[nv] = v
            heappush(pq, (dp[nv] * N) + nv)

first_cost = dp[N - 1]

v = N - 1
while v != 0:
    p = parent[v]
    adj[v][p] = adj[p][v] = uv2d[(v, p)]
    v = p

# pq が持つのは、(コスト * N) + 頂点
# dijkstra 2回目
pq = [N - 1]
dp = [INF] * N
dp[N - 1] = 0
# parent = [-1] * N
while pq:
    cost, v = divmod(heappop(pq), N)
    if cost > dp[v]:
        continue
    for nv, dist in adj[v].items():
        if dp[nv] > dp[v] + dist:
            dp[nv] = dp[v] + dist
            # parent[nv] = v
            heappush(pq, (dp[nv] * N) + nv)

second_cost = dp[0]

print(first_cost + second_cost)