import sys

def solve():
    Gx, Gy, N, F = map(int, input().split())
    x, y, c = [], [], []

    for i in range(N):
        xi, yi, ci = map(int, input().split())
        x.append(xi)
        y.append(yi)
        c.append(ci)

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

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

    for i in range(N):
        for rr in range(Gy, y[i] - 1, -1):
            for cc in range(Gx, x[i] - 1, -1):
                dp[rr][cc] = min(dp[rr][cc], dp[rr - y[i]][cc - x[i]] + c[i])

    print(dp[Gy][Gx])

def debug(x, table):
    for name, val in table.items():
        if x is val:
            print('DEBUG:{} -> {}'.format(name, val), file=sys.stderr)
            return None

if __name__ == '__main__':
    solve()