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
    dist2 = [INF] * n
    dist[start] = 0
    dist2[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, cost2 in graph[v]:
            if dist[v] + cost < dist[nxt_v]:
                dist[nxt_v] = dist[v] + cost
                heapq.heappush(q, (dist[nxt_v], nxt_v))
            elif dist[v] + cost < dist2[nxt_v] and dist[v] + cost >= dist[nxt_v]:
                dist2[nxt_v] = dist[v] + cost
                heapq.heappush(q, (dist2[nxt_v], nxt_v))
            if dist2[v] + cost2 < dist2[nxt_v] and dist[v] + cost2 >= dist[nxt_v]:
                dist2[nxt_v] = dist2[v] + cost2
                heapq.heappush(q, (dist2[nxt_v], nxt_v))
    return dist, dist2


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, d in edges:
    u -= 1
    v -= 1
    graph[u].append((v, cost, d))
    graph[v].append((u, cost, d))

start = 0
dist, dist2 = dijkstra(start, graph)
print(dist[-1] + dist2[-1])