gx,gy,N,F = map(int,input().split())
lsxyz = [list(map(int,input().split())) for i in range(N)]
inf = float('INF')
dp = [[inf]*(gy+1) for i in range(gx+1)]
dp[0][0] = 0

for i in range(gx+1):
    for j in range(gy+1):
        if 0 <= i-1:
            dp[i][j] = min(dp[i][j],dp[i-1][j]+F)
        if 0 <= j-1:
            dp[i][j] = min(dp[i][j],dp[i][j-1]+F)
        for x,y,z in lsxyz:
            if 0 <= i-x and 0 <= j-y:
                dp[i][j] = min(dp[i][j],dp[i-x][j-y]+z)
print(dp[-1][-1])