Problem: You are given two strings s and t consisting of lowercase Latin letters. The length of t is 2 (i.e. this string consists only of two characters).

In one move, you can choose any character of s and replace it with any lowercase Latin letter. More formally, you choose some i and replace s_i (the character at the position i) with some character from 'a' to 'z'.

You want to do no more than k replacements in such a way that maximizes the number of occurrences of t in s as a subsequence.

Recall that a subsequence is a sequence that can be derived from the given sequence by deleting zero or more elements without changing the order of the remaining elements.

Input

The first line of the input contains two integers n and k (2 ≤ n ≤ 200; 0 ≤ k ≤ n) — the length of s and the maximum number of moves you can make. The second line of the input contains the string s consisting of n lowercase Latin letters. The third line of the input contains the string t consisting of two lowercase Latin letters.

Output

Print one integer — the maximum possible number of occurrences of t in s as a subsequence if you replace no more than k characters in s optimally.

Examples

Input


4 2
bbaa
ab


Output


3


Input


7 3
asddsaf
sd


Output


10


Input


15 6
qwertyhgfdsazxc
qa


Output


16


Input


7 2
abacaba
aa


Output


15

Note

In the first example, you can obtain the string "abab" replacing s_1 with 'a' and s_4 with 'b'. Then the answer is 3.

In the second example, you can obtain the string "ssddsdd" and get the answer 10.

In the fourth example, you can obtain the string "aaacaaa" and get the answer 15.

Solution (in PYTHON3):

Solution:
from bisect import *
from collections import *
from math import gcd,ceil,sqrt,floor,inf
from heapq import *
from itertools import *
from operator import add,mul,sub,xor,truediv,floordiv
from functools import *

#------------------------------------------------------------------------
import os
import sys
from io import BytesIO, IOBase
# region fastio

BUFSIZE = 8192
 
class FastIO(IOBase):
    newlines = 0
 
    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None
 
    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()
 
    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()
 
    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)
 
 
class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")
 
 
sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")


#------------------------------------------------------------------------
def RL(): return map(int, sys.stdin.readline().rstrip().split())
def RLL(): return list(map(int, sys.stdin.readline().rstrip().split()))
def N(): return int(input())
#------------------------------------------------------------------------

from types import GeneratorType
 
 
def bootstrap(f, stack=[]):
    def wrappedfunc(*args, **kwargs):
        if stack:
            return f(*args, **kwargs)
        else:
            to = f(*args, **kwargs)
            while True:
                if type(to) is GeneratorType:
                    stack.append(to)
                    to = next(to)
                else:
                    stack.pop()
                    if not stack:
                        break
                    to = stack[-1].send(to)
            return to
 
    return wrappedfunc


farr=[1]
ifa=[]

def fact(x,mod=0):
    if mod:
        while x>=len(farr):
            farr.append(farr[-1]*len(farr)%mod)
    else:
        while x>=len(farr):
            farr.append(farr[-1]*len(farr))
    return farr[x]

def ifact(x,mod):
    global ifa
    ifa.append(pow(farr[-1],mod-2,mod))
    for i in range(x,0,-1):
        ifa.append(ifa[-1]*i%mod)
    ifa=ifa[::-1]

def per(i,j,mod=0):
    if i<j: return 0
    if not mod:
        return fact(i)//fact(i-j)
    return farr[i]*ifa[i-j]%mod
    
def com(i,j,mod=0):
    if i<j: return 0
    if not mod:        
        return per(i,j)//fact(j)
    return per(i,j,mod)*ifa[j]%mod

def catalan(n):
    return com(2*n,n)//(n+1)
    
def linc(f,t,l,r):
    while l<r:
        mid=(l+r)//2
        if t>f(mid):
            l=mid+1
        else:
            r=mid
    return l

def rinc(f,t,l,r):
    while l<r:
        mid=(l+r+1)//2
        if t<f(mid):
            r=mid-1
        else:
            l=mid
    return l

def ldec(f,t,l,r):
    while l<r:
        mid=(l+r)//2
        if t<f(mid):
            l=mid+1
        else:
            r=mid
    return l

def rdec(f,t,l,r):
    while l<r:
        mid=(l+r+1)//2
        if t>f(mid):
            r=mid-1
        else:
            l=mid
    return l

def isprime(n):
    for i in range(2,int(n**0.5)+1):
        if n%i==0:
            return False
    return True

def binfun(x):
    c=0
    for w in arr:
        c+=ceil(w/x)
    return c

def lowbit(n):
    return n&-n

def inverse(a,m):
    a%=m
    if a<=1: return a
    return ((1-inverse(m,a)*m)//a)%m

class BIT:
    def __init__(self,arr):
        self.arr=arr
        self.n=len(arr)-1
        
    def update(self,x,v):
        while x<=self.n:
            self.arr[x]+=v
            x+=x&-x

    def query(self,x):
        ans=0
        while x:
            ans+=self.arr[x]
            x&=x-1
        return ans
'''
class SMT:
    def __init__(self,arr):
        self.n=len(arr)-1
        self.arr=[0]*(self.n<<2)
        self.lazy=[0]*(self.n<<2)
        def Build(l,r,rt):
            if l==r:
                self.arr[rt]=arr[l]
                return
            m=(l+r)>>1
            Build(l,m,rt<<1)
            Build(m+1,r,rt<<1|1)
            self.pushup(rt)
        Build(1,self.n,1)

    def pushup(self,rt):
        self.arr[rt]=self.arr[rt<<1]+self.arr[rt<<1|1]

    def pushdown(self,rt,ln,rn):#lr,rn表区间数字数
        if self.lazy[rt]:
            self.lazy[rt<<1]+=self.lazy[rt]
            self.lazy[rt<<1|1]=self.lazy[rt]
            self.arr[rt<<1]+=self.lazy[rt]*ln
            self.arr[rt<<1|1]+=self.lazy[rt]*rn
            self.lazy[rt]=0
            
    def update(self,L,R,c,l=1,r=None,rt=1):#L,R表示操作区间
        if r==None: r=self.n
        if L<=l and r<=R:
            self.arr[rt]+=c*(r-l+1)
            self.lazy[rt]+=c
            return
        m=(l+r)>>1
        self.pushdown(rt,m-l+1,r-m)
        if L<=m: self.update(L,R,c,l,m,rt<<1)
        if R>m: self.update(L,R,c,m+1,r,rt<<1|1)
        self.pushup(rt)

    def query(self,L,R,l=1,r=None,rt=1):
        if r==None: r=self.n
        #print(L,R,l,r,rt)
        if L<=l and R>=r:
            return self.arr[rt]
        m=(l+r)>>1
        self.pushdown(rt,m-l+1,r-m)
        ans=0
        if L<=m: ans+=self.query(L,R,l,m,rt<<1)
        if R>m: ans+=self.query(L,R,m+1,r,rt<<1|1)
        return ans
'''       
class DSU:#容量+路径压缩
    def __init__(self,n):
        self.c=[-1]*n

    def same(self,x,y):
        return self.find(x)==self.find(y)

    def find(self,x):
        if self.c[x]<0:
            return x
        self.c[x]=self.find(self.c[x])
        return self.c[x]

    def union(self,u,v):
        u,v=self.find(u),self.find(v)
        if u==v:
            return False
        if self.c[u]<self.c[v]:
            u,v=v,u
        self.c[u]+=self.c[v]
        self.c[v]=u
        return True

    def size(self,x): return -self.c[self.find(x)]
    
class UFS:#秩+路径
    def __init__(self,n):
        self.parent=[i for i in range(n)]
        self.ranks=[0]*n

    def find(self,x):
        if x!=self.parent[x]:
            self.parent[x]=self.find(self.parent[x])
        return self.parent[x]

    def union(self,u,v):
        pu,pv=self.find(u),self.find(v)
        if pu==pv:
            return False
        if self.ranks[pu]>=self.ranks[pv]:
            self.parent[pv]=pu
            if self.ranks[pv]==self.ranks[pu]:
                self.ranks[pu]+=1
        else:
            self.parent[pu]=pv

def Prime(n):
    c=0
    prime=[]
    flag=[0]*(n+1)
    for i in range(2,n+1):
        if not flag[i]:
            prime.append(i)
            c+=1
        for j in range(c):
            if i*prime[j]>n: break
            flag[i*prime[j]]=prime[j]
            if i%prime[j]==0: break
    return prime

def dij(s,graph):
    d={}
    d[s]=0
    heap=[(0,s)]
    seen=set()
    while heap:
        dis,u=heappop(heap)
        if u in seen:
            continue
        for v in graph[u]:
            if v not in d or d[v]>d[u]+graph[u][v]:
                d[v]=d[u]+graph[u][v]
                heappush(heap,(d[v],v))
    return d

def GP(it): return [(ch,len(list(g))) for ch,g in groupby(it)]

class DLN:
    def __init__(self,val):
        self.val=val
        self.pre=None
        self.next=None
       

t=1
for i in range(t):
    n,k=RL()
    s=input()
    t=input()
    if t[0]==t[1]:
        c=s.count(t[0])
        c=min(n,c+k)
        print(c*(c-1)//2)
        exit()
    dp=[[[-inf]*(k+1) for i in range(n+1)] for j in range(n)]
    if s[0]==t[0]:
        dp[0][1][0]=0
    else:
        dp[0][0][0]=0
    if k:dp[0][1][1]=0
    for i in range(1,n):
        for j in range(i+2):
            for a in range(k+1):
                if s[i]==t[0]:
                    if j:dp[i][j][a]=max(dp[i][j][a],dp[i-1][j-1][a])
                    if a:
                        dp[i][j][a]=max(dp[i][j][a],dp[i-1][j][a-1]+j)
                elif s[i]==t[1]:
                    dp[i][j][a]=max(dp[i][j][a],dp[i-1][j][a]+j)
                    if a and j:
                        dp[i][j][a]=max(dp[i][j][a],dp[i-1][j-1][a-1])
                else:
                    dp[i][j][a]=max(dp[i][j][a],dp[i-1][j][a])
                    if a:
                        dp[i][j][a]=max(dp[i][j][a],dp[i-1][j][a-1]+j)
                        if j:
                            dp[i][j][a]=max(dp[i][j][a],dp[i-1][j-1][a-1])
    ans=0
    for i in range(n+1):
        for j in range(k+1):
            ans=max(ans,dp[n-1][i][j])
    print(ans)
        
        
''' 
sys.setrecursionlimit(200000)
import threading
threading.stack_size(10**8)
t=threading.Thread(target=main)
t.start()
t.join()
'''