Gx, Gy, n, f = [int(_) for _ in input().split()]

xyc = []
for i in range(n):
    xyc.append([int(_) for _ in input().split()])    

cost_field = [[(i+j)*f for i in range(Gy+1)] for j in range(Gx+1)]
 
warped_xy = [[0, 0]]
for i in range(n):
    for j in range(len(warped_xy)):
        new_cost = cost_field[warped_xy[j][0]][warped_xy[j][1]] + xyc[i][2]
        try:
            if new_cost < cost_field[warped_xy[j][0] + xyc[i][0]][warped_xy[j][1]+ xyc[i][1]]:
                cost_field[warped_xy[j][0] + xyc[i][0]][warped_xy[j][1]+ xyc[i][1]] = new_cost
                cost_field[Gx][Gy] = min(cost_field[Gx][Gy], new_cost + (Gx - (warped_xy[j][0] + xyc[i][0]) + Gy - (warped_xy[j][1] + xyc[i][1]) )* f )
                
                if [warped_xy[j][0] + xyc[i][0], warped_xy[j][1]+ xyc[i][1]] not in warped_xy:
                    warped_xy.append([warped_xy[j][0] + xyc[i][0], warped_xy[j][1]+ xyc[i][1]])
            
        except: pass
      
print(cost_field[Gx][Gy])