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())
a=[input() for i in range(n)]
kol_p,nob=[0],[0]
for i in range(m):
    z=0
    for j in range(n):
        if(a[j][i]=='.'):z+=1
    kol_p+=[z]
    kol_np+=[n-z]
for i in range(1,m+1):
    kol_p[i]+=kol_p[i-1]
    kol_np[i]+=kol_np[i-1]
d=[]
for i in range(0,m+1):
    d+=[[5000000,50000000] ]
d[0][0]=0
d[0][1]=0
for i in range(0,m+1):
    for j in range(x,y+1):
        if((i+j)>m): break
        d[i+j][0]=min(d[i+j][0],d[i][1]+kol_np[i+j]-kol_np[i])
        d[i+j][1]=min(d[i+j][1],d[i][0]+kol_p[i+j]-kol_p[i])
print (min(d[m][0],d[m][1]))
