Gx,Gy,N,F = map(int,input().split())
A = [0]+[list(map(int,input().split())) for _ in range(N)]
dp = [[[3*10**5 for _ in range(Gy+1)] for _ in range(Gx+1)] for _ in range(N+1)]
for j in range(Gx+1):
    for k in range(Gy+1):
        dp[0][j][k] = (j+k)*F
for i in range(1,N+1):
    x,y,c = A[i]
    for j in range(Gx+1):
        for k in range(Gy+1):
            dp[i][j][k] = min((j+k)*F,dp[i-1][j][k])
            if j>=x and k>=y:
                dp[i][j][k] = min(dp[i][j][k],dp[i-1][j-x][k-y]+min(c,(x+y)*F))
print(dp[N][Gx][Gy])