Gx, Gy, N, F = map(int, input().split())
xyc = [tuple(map(int, input().split())) for _ in range(N)]
dp = [[[10 ** 18 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):
        if i == 0 and j == 0:
            dp[0][i][j] = 0
        else:
            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 j == 0 and k == 0:
                dp[i+1][j][k] = 0
                continue
            
            dp[i+1][j][k] = min(dp[i+1][j][k], dp[i][j][k])
            
            if j == 0:
                dp[i+1][j][k] = min(dp[i+1][j][k], dp[i][j][k-1] + F)
            elif k == 0:
                dp[i+1][j][k] = min(dp[i+1][j][k], dp[i][j-1][k] + F)
            else:
                dp[i+1][j][k] = min(dp[i+1][j][k], dp[i][j-1][k] + F, dp[i][j][k-1] + F)
            
            if 0 <= j - xi <= Gx and 0 <= k - yi <= Gy:
                dp[i+1][j][k] = min(dp[i+1][j][k], dp[i][j-xi][k-yi] + ci)

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