You've got an *n* × *m* pixel picture. Each pixel can be white or black. Your task is to change the colors of as few pixels as possible to obtain a barcode picture.

A picture is a barcode if the following conditions are fulfilled: 
 -  All pixels in each column are of the same color. -  The width of each monochrome vertical line is at least *x* and at most *y* pixels. In other words, if we group all neighbouring columns of the pixels with equal color, the size of each group can not be less than *x* or greater than *y*.
The first line contains four space-separated integers *n*, *m*, *x* and *y* (1 ≤ *n*, *m*, *x*, *y* ≤ 1000; *x* ≤ *y*).

Then follow *n* lines, describing the original image. Each of these lines contains exactly *m* characters. Character "." represents a white pixel and "#" represents a black pixel. The picture description doesn't have any other characters besides "." and "#".
n,m,x,y=map(int,input().split())
cnt=[0]*m
for i in range(n):
    s=input()
    for j in range(m):
        if s[j]=='#':
            cnt[j]+=1

pre=[[0,0]]
for i in cnt:
    pre.append([pre[-1][0]+i,pre[-1][1]+n-i])
dp=[None]*(m+1)
dp[0]=[0,0]
for i in range(m):
    dp[i+1]=[int(1e6),int(1e6)]
for i in range(m):
    for j in range(x,y+1):
        try:
            if i+j<=m:
                dp[i+j][0]=min(dp[i][1]+pre[i+j][0]-pre[i][0],dp[i+j][0])
                dp[i+j][1]=min(dp[i+j][1],dp[i][0]+pre[i+j][1]-pre[i][1])
        except:
            print(i,j)
print(min(dp[m][0],dp[m][1]))