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 "#".
import sys
from functools import lru_cache, cmp_to_key
from heapq import merge, heapify, heappop, heappush
from math import *
from collections import defaultdict as dd, deque, Counter as C
from itertools import combinations as comb, permutations as perm
from bisect import bisect_left as bl, bisect_right as br, bisect
from time import perf_counter
from fractions import Fraction
import copy
import time
starttime = time.time()
mod = int(pow(10, 9) + 7)
mod2 = 998244353
# from sys import stdin
# input = stdin.readline
def data(): return sys.stdin.readline().strip()
def out(*var, end="\n"): sys.stdout.write(' '.join(map(str, var))+end)
def L(): return list(sp())
def sl(): return list(ssp())
def sp(): return map(int, data().split())
def ssp(): return map(str, data().split())
def l1d(n, val=0): return [val for i in range(n)]
def l2d(n, m, val=0): return [l1d(n, val) for j in range(m)]
try:
    # sys.setrecursionlimit(int(pow(10,6)))
    sys.stdin = open("input.txt", "r")
    # sys.stdout = open("../output.txt", "w")
except:
    pass


n,m,x,y=L()
A=[input() for i in range(n)]
Z=[]
for j in range(m):
    cnt=0
    for i in range(n):
        if A[i][j]=="#":
            cnt+=1
    Z.append(cnt)

def rec(last,streak,i):
    if i==m:
        return 0
    if last==1:
        if streak<x:
            return n-Z[i]+rec(1,streak+1,i+1)
        elif x<=streak<y:
            return min(n-Z[i]+rec(1,streak+1,i+1),n+rec(0,0,i+1)) 
        elif streak==y:
            return Z[i]+rec(0,0,i+1)
    else:
        return min(n-Z[i]+rec(1,1,i+1),Z[i]+rec(0,0,i+1))   



ans=min(n-Z[0]+rec(1,1,1),Z[0]+rec(0,0,1))
print(ans)







endtime = time.time()
# print(f"Runtime of the program is {endtime - starttime}")
