Gx, Gy, N, F = map(int, input().split())
xyc = [tuple(map(int, input().split())) for _ in range(N)]
dp = [[[0 for _ in range(Gy+1)] for _ in range(Gx+1)] for _ in range(N+1)]

for i in range(Gx+1):
    for j in range(Gy+1):
        dp[0][i][j] = (i + j) * F

for i in range(N):
    xi, yi, ci = xyc[i]
    for j in range(Gx+1):
        for k in range(Gy+1):
            if 0 <= j - xi <= Gx and 0 <= k - yi <= Gy:
                dp[i+1][j][k] = min(dp[i][j][k], dp[i][j-xi][k-yi] + ci)
            else:
                dp[i+1][j][k] = dp[i][j][k]

print(dp[N][Gx][Gy])