import heapq
import sys
input = sys.stdin.buffer.readline


def dijkstra(start: int, graph: list) -> list:
    """dijkstra法: 始点startから各頂点への最短距離を求める
    計算量: O((E+V)logV)
    """
    INF = 10 ** 18
    n = len(graph)
    dist = [INF] * n
    dist[start] = 0
    q = [(0, start)] # q = [(startからの距離, 現在地)]
    while q:
        d, v = heapq.heappop(q)
        if dist[v] < d:
            continue
        for nxt_v, cost in graph[v]:
            if dist[v] + cost < dist[nxt_v]:
                dist[nxt_v] = dist[v] + cost
                heapq.heappush(q, (dist[nxt_v], nxt_v))
    return dist


n, m = map(int, input().split())
edges = [list(map(int, input().split())) for _ in range(m)]
ans = 0


graph = [[] for i in range(n)]
for u, v, cost, _ in edges:
    u -= 1
    v -= 1
    graph[u].append((v, cost))
    graph[v].append((u, cost))

start = n - 1
dist = dijkstra(start, graph)
ans += dist[0]

path = [0]
v = 0
while v != n - 1:
    for prv_v, cost in graph[v]:
        if dist[prv_v] + cost == dist[v]:
            path.append(prv_v)
            v = prv_v
            break

mapping = set([])
for u, v in zip(path, path[1:]):
    mapping.add((u, v))
    mapping.add((v, u))


graph = [[] for i in range(n)]
for u, v, c, d in edges:
    u -= 1
    v -= 1
    if (u, v) in mapping:
        graph[u].append((v, d))
        graph[v].append((u, d))
    else:
        graph[u].append((v, c))
        graph[v].append((u, c))

start = 0
dist = dijkstra(start, graph)
ans += dist[-1]

print(ans)