#include<bits/stdc++.h>
using namespace std;

#define rep(i,a,b) for(ll i=a,i##end=b;i<=i##end;++i)
using ll = long long;
const ll P=998244353;

const ll M=2e6+10;
ll A[M],B[M],C[M],pw[M],dp[M],v[M];
char s1[M],s2[M];
ll Pow(ll a,ll b){
	ll res=1;
	for(;b;b>>=1,a=a*a%P)
		if(b&1)res=res*a%P;
	return res;
}
const ll * ntt_init_w(const ll &n){
	static const  ll *w[M];
	if(w[n]==NULL){
		ll *wn=new ll[n];
		wn[0]=1;
		if(n>1){
			ll w0=Pow(3,(P-1)/(n<<1));
			const ll *wm=ntt_init_w(n>>1);
			for(ll i=0;i<n;i+=2)
				wn[i+1]=1ll*(wn[i]=wm[i>>1])*w0%P;
		}
		w[n]=wn;
	}
	return w[n];
}
void NTT(ll *a,ll n,ll ty){
	for(ll i=0,j=0;i<n;i++){
		if(i<j)swap(a[i],a[j]);
		for(ll k=n>>1;(j^=k)<k;k>>=1);
	}
	for(ll i=1;i<n;i<<=1){
		const ll *w=ntt_init_w(i);
		for(ll j=0;j<n;j+=i<<1)
			for(ll k=j;k<j+i;k++){
				const ll t1=a[k],t2=1ll*a[k+i]*w[k-j]%P;
				a[k]=t1+t2<P?t1+t2:t1+t2-P;
				a[k+i]=t1<t2?t1-t2+P:t1-t2;
			}
	}
	if(ty==1)return ;
	reverse(a+1,a+n);
	const ll inv=Pow(n,P-2);
	for(ll i=0;i<n;++i)a[i]=1ll*a[i]*inv%P;
}
int main(){
	ll o,k;
	scanf("%lld%lld",&o,&k);
	scanf("%s%s",s1+1,s2+1);
	ll l1=strlen(s1+1);
	ll l2=strlen(s2+1);
	for(ll i=1;i<=l1;++i)
		v[i]=v[i-1]+(s1[i]=='o'?o:k);		
	rep(i,1,l1)if(s1[i]=='o')A[i]=1;
	rep(i,1,l2)if(s2[i]=='k')B[l2-i]=1;
	ll len=1;
	while(len<l1+l2+3)len<<=1;
	NTT(A,len,1),NTT(B,len,1);
	rep(i,0,len-1)A[i]=A[i]*B[i]%P;
	
	NTT(A,len,-1);
	rep(i,1,l1)C[i]+=A[i];
	memset(A,0,sizeof A);
	memset(B,0,sizeof B);
	rep(i,1,l1)if(s1[i]=='k')A[i]=1;
	rep(i,1,l2)if(s2[i]=='o')B[l2-i]=1;
	NTT(A,len,1),NTT(B,len,1);
	rep(i,0,len-1)A[i]=A[i]*B[i]%P;
	NTT(A,len,-1);
	rep(i,1,l1)C[i]+=A[i];
	rep(i,1,l1){
		dp[i]=dp[i-1];
		if(i>=l2&&C[i]<=35){
			dp[i]=max(dp[i],dp[i-l2]+((v[i]-v[i-l2])>>C[i]));
		}
	}
	printf("%lld\n",dp[l1]);
	return 0;
}