#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>#include <vector>#include <map>#include <utility>#include <queue>#include <stack>using namespace std;typedef pair<int,int> pii;const int INF=1<<30;const double eps=1e-6;const int N = 100010;char s[N],a[N],b[N],c[N];bool vis[N][30];int n,k,cnt[N];void rev(char *s){ int l=0,r=n-1; for(;l<r;l++,r--) swap(s[l],s[r]);}void read(){ memset(vis,0,sizeof(vis)); memset(cnt,0,sizeof(cnt)); while(k--) { scanf("%s",s); rev(s); for(int i=0;i<n;++i) vis[i][s[i]-'a']=1; } for(int i=0;i<n;++i) for(int j=0;j<26;++j) if(!vis[i][j]) cnt[i]++;}int ctoint(int idx,char c){ c = c-'a'; int res=0; for(int i=0;i<c;++i) if(!vis[idx][i]) res++; return res;}char inttoc(int idx,int x){ int i; for(i=0;;i++) if(!vis[idx][i] && (x--)==0) break; return i+'a';}void run(){ read(); scanf("%s%s",a,b); rev(a); rev(b); int rem=0,tmp; for(int i=0;i<n;++i) { tmp = rem + ctoint(i,a[i]) + ctoint(i,b[i]); c[i] = tmp%cnt[i]; rem = tmp/cnt[i]; } for(int i=0;i<n;++i) c[i] = inttoc(i,c[i]); for(int i=n-1;i>=0;--i) putchar(c[i]); puts("");}int main(){ while(scanf("%d%d",&n,&k)!=EOF) run(); return 0;}
