gx, gy, N, F = map(int, input().split())
cr = []
for i in range(N):
    x, y, c = map(int, input().split())
    if (x+y)*F > c:
        cr.append([x, y, c])
dp = [[[float('inf')]*(gy+1) for _ in range(gx+1)] for _ in range(len(cr)+1)]
dp[0][0][0] = 0
for i in range(1, len(cr)+1):
    for j in range(gx+1):
        for k in range(gy+1):
            dp[i][j][k] = min(dp[i][j][k], dp[i-1][j][k])
            x, y, c = cr[i-1]
            if j+x<=gx and k+y<=gy:
                dp[i][j+x][k+y] = min(dp[i][j+x][k+y], dp[i-1][j][k]+c)
res = float('inf')
for i in range(gx+1):
    for j in range(gy+1):
        res = min(res, dp[-1][i][j]+(gx-i+gy-j)*F)
print(res)