#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
int o , k;
string s , t;
const int mod=998244353;
inline int inc(int x,int y){return x+y>=mod?x+y-mod:x+y;}
inline int dec(int x,int y){return x-y<0?x-y+mod:x-y;}
inline int mul(int x,int y){return (ll)x*y%mod;}
inline int qpow(int x,int y){
	int res=1;
	for(;y;y>>=1)res=y&1?mul(res,x):res,x=mul(x,x);
	return res;
}
inline int inv(int x){return qpow(x,mod-2);}

const int N=1<<19;
namespace NTT{
int re[N],w[2][N];
inline int getre(int n){
	int len=1,bit=0;
	while(len<n)len<<=1,++bit;
	for(int i=1;i<len;++i)re[i]=(re[i>>1]>>1)|((i&1)<<(bit-1));
	w[0][0]=w[1][0]=1,w[0][1]=qpow(3,(mod-1)/len),w[1][1]=inv(w[0][1]);
	for(int o=0;o<2;++o)for(int i=2;i<len;++i)
		w[o][i]=mul(w[o][i-1],w[o][1]);
	return len;
}
inline void NTT(int* a,int n,int o=0){
	for(int i=1;i<n;++i)if(i<re[i])swap(a[i],a[re[i]]);
	int R;
	for(int k=1;k<n;k<<=1)
		for(int i=0,t=k<<1,st=n/t;i<n;i+=t)
			for(int j=0,nw=0;j<k;++j,nw+=st)
				R=mul(a[i+j+k],w[o][nw]),a[i+j+k]=dec(a[i+j],R),a[i+j]=inc(a[i+j],R);
	if(o){
		R=inv(n);
		for(int i=0;i<n;++i)a[i]=mul(a[i],R);
	}
}

int t0[N],t1[N],t2[N];
inline void multi(const int* a,const int* b,int* c,int n,int m){
	if(n+m<=32){
		memset(c,0,sizeof(int)*(n+m+1));
		for(int i=0;i<=n;++i)
			for(int j=0;j<=m;++j)
				c[i+j]=inc(c[i+j],mul(a[i],b[j]));
		return;
	}
	int len=getre(n+m+1);
	memset(t0,0,sizeof(int)*len),memcpy(t0,a,sizeof(int)*(n+1));
	memset(t1,0,sizeof(int)*len),memcpy(t1,b,sizeof(int)*(m+1));
	NTT(t0,len),NTT(t1,len);
	for(int i=0;i<len;++i)t0[i]=mul(t0[i],t1[i]);
	NTT(t0,len,1);
	memcpy(c,t0,sizeof(int)*(n+m+1));
}

}
int p[N] , q[N];
int p3[N] , q3[N];
int p2[N] , q2[N];
int ans[N];
int sum[250005];
int val[250005];
int dp[250005];
int main()
{
   // freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    ios::sync_with_stdio(false) ; cin.tie(0) ; cout.tie(0);
    cin >> o >> k;
    cin >> s >> t;
    for(int i = 0;i < s.size();i++) {
        if(s[i] == 'o') p[i] = 1;
        else p[i] = 2;
        p2[i] = 1LL*p[i]*p[i];
        p3[i] = p2[i] * p[i];
        if(i != 0) sum[i] = sum[i - 1];
        if(s[i] == 'o') sum[i] += o;
        else sum[i] += k;
    }
    for(int i = 0;i < t.size();i++) {
        if(t[i] == 'o') q[i] = 1;
        else if(t[i] == 'k') q[i] = 2;
        else q[i] = 0;
        q2[i] = 1LL*q[i]*q[i];
        q3[i] = 1LL*q2[i]*q[i];
    }
    int n = s.size() , m = t.size() ;
    for(int i = 0;i < m - i - 1;i++) {
        swap(q[i] , q[m - i - 1]);
        swap(q2[i] , q2[m - i - 1]);
        swap(q3[i] , q3[m - i - 1]);
    }
    int len = NTT::getre(n + m - 1) ;
    NTT::NTT(p , len);
    NTT::NTT(q , len);
    NTT::NTT(p2 , len);
    NTT::NTT(q2 , len);
    NTT::NTT(p3 , len);
    NTT::NTT(q3 , len);
    for(int i = 0;i < len;i++) {
        ans[i] = (1LL*q3[i]*p[i] - 2LL*q2[i]*p2[i]%mod + mod + 1LL*q[i]*p3[i]) % mod;
    }
    NTT::NTT(ans , len , 1);
    for(int i = m - 1;i < len;i++) {
        int s_mat = i - (m - 1);
        if(s_mat + m - 1 >= n) break;
        int x = ans[i] / 2;
        //printf("Mat start %d , %d \n",s_mat , x );
        int v;
        if(x <= 31) {
            if(s_mat == 0) v = sum[s_mat + m - 1];
            else v = (sum[s_mat + m - 1] - sum[s_mat - 1 ]);
            v >>= x;
        }
        else v = 0;

        val[s_mat + m] = v;
    }
    for(int i = 1;i <= n;i++) {
        dp[i] = dp[i - 1];
        if(i - m + 1 >= 0) dp[i] = max(dp[i] , val[i] + dp[i - m ]) ;
    }
    cout << dp[n] << '\n';
    return 0;
}