import heapq

def solve():
    import sys
    input = sys.stdin.read
    data = input().split()
    idx = 0
    n = int(data[idx]); idx +=1
    m = int(data[idx]); idx +=1
    S = int(data[idx]); idx +=1
    T = int(data[idx]); idx +=1
    
    adj = [[] for _ in range(n)]
    for _ in range(m):
        u = int(data[idx]); idx +=1
        v = int(data[idx]); idx +=1
        d = int(data[idx]); idx +=1
        c = int(data[idx]); idx +=1
        adj[u].append((v, d, c))
        adj[v].append((u, d, c))
    
    INF = float('inf')
    dist = [INF] * n
    cost = [INF] * n
    dist[S] = 0
    cost[S] = 0
    heap = []
    heapq.heappush(heap, (0, 0, S))
    
    while heap:
        current_dist, current_cost, u = heapq.heappop(heap)
        if u == T:
            print(current_cost)
            return
        if current_dist > dist[u] or (current_dist == dist[u] and current_cost > cost[u]):
            continue
        for v, d, c in adj[u]:
            new_dist = current_dist + d
            new_cost = current_cost + c
            if new_dist < dist[v]:
                dist[v] = new_dist
                cost[v] = new_cost
                heapq.heappush(heap, (new_dist, new_cost, v))
            elif new_dist == dist[v] and new_cost < cost[v]:
                cost[v] = new_cost
                heapq.heappush(heap, (new_dist, new_cost, v))
    
    print(-1)

solve()