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))

INF = 10**18
dp = [[INF]*(gx+1) for i in range(gy+1)]
dp[0][0] = 0
for i in range(gy+1):
    for j in range(gx+1):
        for di, dj in (1, 0), (0, 1):
            ni, nj = i+di, j+dj
            if 0 <= ni <= gy and 0 <= nj <= gx:
                dp[ni][nj] = min(dp[ni][nj], dp[i][j]+f)
for x, y, c in XYC:
    for i in reversed(range(gy+1)):
        for j in reversed(range(gx+1)):
                if 0 <= i+y <= gy and 0 <= j+x <= gx:
                    dp[i+y][j+x] = min(dp[i+y][j+x], dp[i][j]+c)
print(dp[gy][gx])