def read_data():
    Gx, Gy, N, F = map(int, input().split())
    xyc = []
    for i in range(N):
        x, y, c = map(int, input().split())
        xyc.append((x, y, c))
    return Gx, Gy, N, F, xyc

def solve(Gx, Gy, N, F, xyc):
    inf = float('inf')
    dp = [[inf] * (Gy + 1) for _ in range(Gx + 1)]
    dp[0][0] = 0
    for dx, dy, c in xyc:
        for x in range(Gx - dx, -1, -1):
            for y in range(Gy - dy, -1, -1):
                if dp[x][y] == inf:
                    continue
                prev_cost = dp[x + dx][y + dy]
                new_cost  = dp[x][y] + c
                if prev_cost > new_cost:
                    dp[x + dx][y + dy] = new_cost
    min_cost = (Gx + Gy) * F
    for x in range(Gx + 1):
        for y in range(Gy + 1):
            min_cost = min(min_cost, dp[x][y] + (Gx - x + Gy - y) * F)
    return min_cost

Gx, Gy, N, F, xyc = read_data()
print(solve(Gx, Gy, N, F, xyc))