#include #include using namespace std; using namespace atcoder; typedef long long int ll; typedef long double ld; typedef vector vi; typedef vector vvi; typedef vector vvvi; typedef vector vvvvi; typedef vector vb; typedef vector vvb; typedef vector vvvb; typedef vector vvvvb; typedef pair pi; typedef pair ppi; typedef pair pppi; typedef pair ppppi; #define FOR(i,l,r) for(ll i=l;i=l;i--) #define RREP(i,n) RFOR(i,0,n) #define ALL(x) x.begin(),x.end() #define F first #define S second #define BS(A,x) binary_search(ALL(A),x) #define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin()) #define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin()) #define COU(A,x) (UB(A,x)-LB(A,x)) #define sz(c) ((ll)(c).size()) /* #include namespace mp=boost::multiprecision; using Bint=mp::cpp_int; */ templateusing min_priority_queue=priority_queue,greater>; templateostream&operator<<(ostream&os,pairp){os<istream&operator>>(istream&is,pair&p){is>>p.F>>p.S;return is;} templateostream&operator<<(ostream&os,vectorv){REP(i,sz(v))os<istream&operator>>(istream&is,vector&v){for(T&in:v)is>>in;return is;} templatebool chmax(T&a,T b){if(abool chmin(T&a,T b){if(b(a,b); auto y=convolution(a,b); auto z=convolution(a,b); vectorret(sz(a)+sz(b)-1); REP(i,sz(ret)){ ll v1=(y[i]-x[i])*m1_inv_m2%m2;if(v1<0)v1+=m2; ll v2=(z[i]-(x[i]+m1*v1)%m3)*m12_inv_m3%m3;if(v2<0)v2+=m3; ret[i]=(x[i]+m1*v1+m12_mod*v2)%mod; } return ret; } const ld EPS=1e-8; //* using mint=modint998244353; const ll mod=998244353; //*/ /* using mint=modint1000000007; const ll mod=1000000007; //*/ //using mint=modint; //* typedef vector vm; typedef vector vvm; typedef vector vvvm; typedef vector vvvvm; ostream&operator<<(ostream&os,mint a){os<>(istream&is,mint&a){int x;is>>x;a=mint(x);return is;} //*/ int main(){ ll L,K;string S,T;cin>>L>>K>>S>>T; vi A(26);cin>>A; mint sum=0; REP(i,26)sum+=A[i]; vm B(26); REP(i,26)B[i]=A[i]/sum; vvvm DP(K+1,vvm(L,vm(2*L+1))); DP[0][0][L]=1; REP(i,K){ REP(j,L){ DP[i+1][j][0]+=DP[i][j][0]; DP[i+1][j][2*L]+=DP[i][j][2*L]; FOR(k,1,2*L){ ll a=S[j]-'a',b=T[(j+k)%L]-'a'; if(a==b){ DP[i+1][j][k]+=DP[i][j][k]*(1-B[a]); DP[i+1][(j+1)%L][k]+=DP[i][j][k]*B[a]; } else{ DP[i+1][j][k]+=DP[i][j][k]*(1-B[a]-B[b]); DP[i+1][(j+1)%L][k-1]+=DP[i][j][k]*B[a]; DP[i+1][j][k+1]+=DP[i][j][k]*B[b]; } } } } mint a=0,b=0; REP(i,L)a+=DP[K][i][0],b+=DP[K][i][2*L]; cout<