import heapq
INF=10**20
def Dijkstra(graph, start):
  dist=[INF]*len(graph)
  parent=[INF]*len(graph)
  queue=[(0, start, INF)]
  while queue:
    path_len, v, parent1=heapq.heappop(queue)
    if dist[v]==INF: 
      dist[v]=path_len
      parent[v]=parent1
      for w in graph[v]:
        if dist[w[0]]==INF:      
          heapq.heappush(queue, (dist[v]+w[1], w[0], v))         
  return (dist,parent)
n,m=map(int,input().split())
graph=[]
for i in range(n):
  graph.append([])
edges=[]
for _ in range(m):
  u,v,c,d=map(int,input().split())
  edges.append([u,v,c,d])
  graph[u-1].append((v-1,c))
  graph[v-1].append((u-1,c))
dist,parent=Dijkstra(graph,0)
ans=dist[n-1]
point=n-1
used=set()
while point!=0:
  used.add(parent[point]*(10**10)+point)
  used.add(point*(10**10)+parent[point])
  point=parent[point]
graph=[]
for i in range(n):
  graph.append([])
for i in range(m):
  u=edges[i][0]
  v=edges[i][1]
  c=edges[i][2]
  d=edges[i][3]
  if (u-1)*(10**10)+(v-1) in used:
    graph[u-1].append([v-1,d])
    graph[v-1].append([u-1,d])
  else:
    graph[u-1].append([v-1,c])
    graph[v-1].append([u-1,c])
dist,parent=Dijkstra(graph,0)
ans+=dist[n-1]
print(ans)