#O(ElogV),頂点数10**5以上の場合は避ける
import heapq
def dijkstra_heap(s,edge):
  N = len(edge)
  dists = [float('inf')] * N #始点sから各頂点への最短距離
  prev = [-1]*N
  used = [False] * N
  dists[s] = 0
  used[s] = True
  vlist = []
  #vlist : [sからの暫定(未確定)最短距離,頂点]のリスト
  #edge[s] : sから出る枝の[重み,終点]のリスト
  for v,d in edge[s]:
    heapq.heappush(vlist,(d,s,v)) #sの隣の点は枝の重さがそのまま暫定最短距離となる
  while len(vlist):
    #まだ使われてない頂点の中から最小の距離のものを探す→確定させる
    d,u,v = heapq.heappop(vlist)
    #[d,v]:[sからの(確定)最短距離,頂点]
    if used[v]:
      continue
    dists[v] = d
    prev[v] = u
    used[v] = True
    for w,d in edge[v]:
      if not used[w]:
        heapq.heappush(vlist,(dists[v]+d,v,w))
  return dists, prev

import sys,os,io
input = sys.stdin.readline
#input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline
N, M = map(int, input().split())
edge = [[] for _ in range(N)]
edges = {}
after = {}
for i in range(M):
  u,v,c,d = map(int, input().split())
  u -= 1
  v -= 1
  edge[u].append((v,c))
  edge[v].append((u,c))
  edges[(u,v)] = c
  edges[(v,u)] = c
  after[(u,v)] = d
  after[(v,u)] = d
dists1, prev1 = dijkstra_heap(0, edge)
ans = dists1[-1]
v = N-1
while v!=0:
  w = prev1[v]
  edges[(w,v)] = after[(w,v)]
  edges[(v,w)] = after[(v,w)]
  v = w
new_edge = [[] for _ in range(N)]
for i in range(N):
  for v,c in edge[i]:
    new_edge[i].append((v,edges[(i,v)]))
dists2, prev2 = dijkstra_heap(0,new_edge)
ans += dists2[-1]
print(ans)