class Heap_Point:
        def __init__(self,x,d):
            self.d=d
            self.x=x

        def __str__(self):
            return "(point:{}, dist:{})".format(self.x,self.d)

        def __repr__(self):
            return str(self)

        def __lt__(self,other):
            return self.d<other.d

        def __iter__(self):
            yield from (self.x,self.d)
#================================================
from heapq import heappop,heappush

Gx,Gy,N,F=map(int,input().split())
P=["*"]
for _ in range(N):
    x,y,c=map(int,input().split())
    P.append((x,y,c))

inf=float("inf")
T=[[[inf]*(N+1) for _ in range(Gy+1)] for __ in range(Gx+1)]
T[0][0][0]=0
Q=[Heap_Point((0,0,0),0)]

while Q:
    p,d=heappop(Q)
    x,y,k=p

    if x==Gx and y==Gy:
        break

    if T[x][y][k]<d:
        continue

    if x<Gx and T[x+1][y][k]>d+F:
        T[x+1][y][k]=d+F
        heappush(Q,Heap_Point((x+1,y,k),d+F))

    if y<Gy and T[x][y+1][k]>d+F:
        T[x][y+1][k]=d+F
        heappush(Q,Heap_Point((x,y+1,k),d+F))

    for i,q in enumerate(P[k+1:],k+1):
        a,b,c=q
        if 0<=x+a<=Gx and 0<=y+b<=Gy and T[x+a][y+b][i]>d+c:
            T[x+a][y+b][i]=d+c
            heappush(Q,Heap_Point((x+a,y+b,i),d+c))

print(min(T[Gx][Gy]))