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=[int(e) for e in input().split()]
a=[[e=="#" for e in input()] for i in range(n)]
c=[sum(a[j][i] for j in range(n)) for i in range(m)]
inf=10**18
F=[[[inf]*2 for k in range(y+1)] for i in range(m)]
F[x-1][x][0]=sum(c[i] for i in range(x))
F[x-1][x][1]=n-sum(c[i] for i in range(x))
for i in range(x,m):
    F[i][1][0]=c[i]+min(F[i-1][k][1] for k in range(x,y+1))
    F[i][1][1]=n-c[i]+min(F[i-1][k][0] for k in range(x,y+1))
    for k in range(2,y+1):
        F[i][k][0]=c[i]+F[i-1][k-1][0]
        F[i][k][1]=n-c[i]+F[i-1][k-1][1]
print(min( min(F[-1][k][0],F[-1][k][1]) for k in range(x,y+1) ))