# V: 頂点数
# g[v] = {(w, cost)}:
#     頂点vから遷移可能な頂点(w)とそのコスト(cost)
# r: 始点の頂点

from heapq import heappush, heappop
INF = 10**18
def dijkstra(N, G, s):
    dist = [INF] * N
    que = [(0, s)]
    dist[s] = 0
    while que:
        c, v = heappop(que)
        if dist[v] < c:
            continue
        for t, cost in G[v]:
            if dist[v] + cost < dist[t]:
                dist[t] = dist[v] + cost
                heappush(que, (dist[t], t))
    return dist

N, M = map(int, input().split())
G = [set() for _ in range(N)]
vs = list()
X = []
for _ in range(M):
    a, b, c, d = map(int, input().split())
    a-=1;b-=1
#    if a==0:
#        R = min(c+d, R)
#        vs.append((b, c, d))
    G[a].add((b, c))
    G[b].add((a, c))
    X.append((a, b, c, d))
dd = dijkstra(N, G, 0)
ans = dd[N-1]

c = N-1
k = 0
R = [N-1]
while 1:
    mn = 10**18
    rr = -1
    for u, co in G[c]:
        if dd[u]+co < mn:
            mn = co+dd[u]
            rr = u
    R.append(rr)
    c = rr
    if rr == 0:
        break
    
G2 = [set() for _ in range(N)]
vs = set()
for u, v in zip(R, R[1:]):
    vs.add((u, v))
    vs.add((v, u))
for a, b, c, d in X:
    if (a, b) in vs:
        G2[a].add((b, d))
        G2[b].add((a, d))
    else:
        G2[a].add((b, c))
        G2[b].add((a, c))

dd = dijkstra(N, G2, N-1)
ans += dd[0]

print(ans)