import sys
from heapq import * 

input = sys.stdin.readline

INF = float("inf")

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, 頂点)
# dijkstra 1回目
pq = [(0, 0)]
dp = [INF] * N
dp[0] = 0
parent = [-1] * N
while pq:
    cost, v = heappop(pq)
    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], nv))
# print(dp)
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, 頂点)
# dijkstra 2回目
pq = [(dp[N - 1], N - 1)]
for i in range(N - 1):
    dp[i] = INF
# parent = [-1] * N
while pq:
    cost, v = heappop(pq)
    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], nv))
# print(dp)
print(dp[0])