#include<map>

#include<queue>

#include<vector>

#include<cmath>

#include<string>

#include<cstdio>

#include<cstring>

#include<iostream>

#include<algorithm>

#define Maxn 100010

#define inf 1<<30

using namespace std;

map<int,int> g;

int ans,n,ha[],Exp[];

char s[];

int tar;

struct QT{

    int val,st;

    int operator <(const QT &temp) const{

        return st>temp.st;

    }

};

priority_queue<QT> q;

int bfs(int temp)

{

    int i,j,str;

    while(!q.empty()) q.pop();

    QT tt,p;

    tt.val=temp,tt.st=;

    q.push(tt);

    while(!q.empty()){

        p=q.top();

        q.pop();

        str=p.val;

        if(str==tar) return p.st;

        int a,b;

        a=str/Exp[n-];

        b=str%Exp[n-]/Exp[n-];

        temp=b*Exp[n-]+a*Exp[n-]+str%Exp[n-];

        if(!g[temp]){

            tt.val=temp,tt.st=p.st+;

            q.push(tt);

            g[temp]=;

        }

        temp=str%Exp[n-]*+str/Exp[n-];

        if(!g[temp]){

            tt.val=temp,tt.st=p.st+;

            q.push(tt);

            g[temp]=;

        }

    }

}

int main()

{

    char str[];

    int i,j;

    ha['A']=;

    ha['G']=;

    ha['C']=;

    ha['T']=;

    Exp[]=;

    for(int i=;i<;i++)

        Exp[i]=Exp[i-]*;

    while(scanf("%d",&n)!=EOF){

        ans=inf;

        g.clear();

        scanf("%s%s",str,s);

        tar=;

        int temp=;

        for(i=;i<n;i++){

            tar=tar*+ha[s[i]];

            temp=temp*+ha[str[i]];

        }

        printf("%d\n",bfs(temp));

    }

    return ;

}