#include<bits/stdc++.h>
using namespace std;
typedef struct node
{
struct node *lchild;
struct node *rchild;
char data;
} node ,*tree;
int treedeep(tree &t)
{
int ld,rd;
if(!t)
return 0;
else
{
ld=treedeep(t->lchild);
rd=treedeep(t->rchild);
if(ld>rd)
return ld+1;
else
return rd+1;
}
}
tree treetrans(char *s,char *r,int n)
{
tree t;
char *p;
if(n==0)
return NULL;
t=new(node);
if(!t)
exit(0);
t->data=s[0];
for(p=r; p!='\0'; p++)
{
if(*p==s[0])
{
break;
}
}
int ln=p-r;
t->lchild=treetrans(s+1,r,ln);
t->rchild=treetrans(s+ln+1,p+1, n-ln-1);
return t;
}
int main()
{
int n;
tree tre;
char s[60],r[60];
while(cin>>n)
{
tre=new(node);
cin>>s;
cin>>r;
tre=treetrans(s,r,n);
cout<<treedeep(tre)<<endl;
}
}