def calc_score(c, i, x, y, max_x, max_y, score, F):
    if i == len(c):
        return F * (max_x + max_y - x - y) + score
    elif c[i][0] + x > max_x or c[i][1] + y > max_y:
        return calc_score(c, i+1, x, y, max_x, max_y, score, F)
    else:
        return min(calc_score(c, i+1, x, y, max_x, max_y, score, F), calc_score(c, i+1, x+c[i][0], y+c[i][1], max_x, max_y, score+c[i][2], F))

X, Y, N, F = list(map(int, input().split()))
c = []

for i in range(N):
    tmp = list(map(int, input().split()))
    #if (tmp[0] + tmp[1]) * F <= tmp[2]:
    #    continue
    c.append(tmp)

if len(c):
    score = calc_score(c, 0, 0, 0, X, Y, 0, F)
else:
    score = F * (X + Y)

print(score)