#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,m,al=0,bl=0,z=1;
	char a[100001],b[100001];
	cin>>n>>m>>a>>b;
	for(int i=0;i<n;i++){
		if(a[i]=='#'){
			al++;
		}
	}
	bl=m-al;
	if(bl<26){
		for(int i=0;i<n;i++){
			if(a[i]=='#'){
				a[i]='a'+z-1;
				z++;
			}
		}
	}else{
		for(int i=0;i<n;i++){
			if(z==1){
				if(a[i]=='#'){
					a[i]='a';
					z++;
				}
			}else if(bl>=26&&a[i]=='#'){
					a[i]='a';
					bl-=26;
			}else{
				if(a[i]=='#'){
					a[i]='a'+z-1;
					z++;
				}
			}
			z=(z-1)%26+1;
		}
	}
	cout<<a;
	return 0;
}