from collections import deque
n,m = map(int,input().split())
e = [[] for i in range(n+1)]
for i in range(m):
    u,v,c,d = map(int,input().split())
    e[u].append([v,c,d])
    e[v].append([u,c,d])
dis = [10**20]*(n+1)
dis[1] = 0
par = [-1]*(n+1)
q = deque([1])
while q:
    now = q.popleft()
    for nex,c,d in e[now]:
        if dis[nex] > dis[now]+c:
            dis[nex] = dis[now]+c
            par[nex] = now
            q.append(nex)
ans = dis[n]
now = n
while par[now] != -1:
    p = par[now]
    for i in range(len(e[now])):
        if e[now][i][0] == p:
            e[now][i][1] = -1
            break
    now = p
dis = [10**20]*(n+1)
dis[n] = 0
q = deque([n])
while q:
    now = q.popleft()
    for nex,c,d in e[now]:
        if c == -1:
            if dis[nex] > dis[now]+d:
                dis[nex] = dis[now]+d
                q.append(nex)
        else:
            if dis[nex] > dis[now]+c:
                dis[nex] = dis[now]+c
                q.append(nex)
ans += dis[1]
print(ans)