#pragma GCC optimize("Ofast","unroll-loops","omit-frame-pointer","inline")
#pragma GCC option("arch=native","tune=native","no-zero-upper")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2")
#pragma GCC optimize(3)
#include<bits/stdc++.h>
using namespace std;
const int N = 250009;
int n,o,k,dp[N],so[N],sk[N];
char s[N],t[N];
bitset<N>oo,kk,op,kp,c,d;
int qj(int x,int y){
	while(y){
		if(!x) return 0;
		x/=2;
		y--;
	}
	return x;
}

int main(){
//	freopen("G.in","r",stdin);
	scanf("%d%d",&o,&k);
	scanf("%s%s",s,t);
	n=strlen(s);int m=strlen(t);
	for(int i=0;i<n;i++){
		if(s[i]=='o') oo[i+1]=1;
		else kk[i+1]=1;
		so[i+1]=so[i]+(s[i]=='o'?o:0);
		sk[i+1]=sk[i]+(s[i]=='k'?k:0);
	}
	for(int i=0;i<m;i++){
		if(t[i]=='?') op[i+1]=kp[i+1]=1;
		if(t[i]=='o') op[i+1]=1;
		if(t[i]=='k') kp[i+1]=1;
	}
//	for(int i=1;i<=n;i++) cout<<kk[i];puts("");
	for(int i=m;i<=n;i++){
		int num=m-(op&oo).count()-(kp&kk).count();
//		printf("%d %d %d %d\n",i,num,(op&oo).count(),(kp&kk).count());
		dp[i]=max(dp[i-1],dp[i-m]+qj(so[i]-so[i-m]+sk[i]-sk[i-m],num));
//		printf("%d\n",dp[i]);
		oo>>=1,kk>>=1;
	}
	printf("%d\n",dp[n]);
	return 0;
}