#include<bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pr pair<int,int>
#define _(x,y) x=(x+y)%mod
#define ll long long
int read(){int d=1,k=0;char c=getchar();
while(!(c>='0' and c<='9' or c=='-'))c=getchar();if(c=='-')d=-1,c=getchar();
while(c>='0' and c<='9')k=(k<<3)+(k<<1)+(c^48),c=getchar();return d*k;}
#define N 800105
#define M 800110
int cnt[M],id[M],rk[M],ork[M],sa[M],height[M],ans,st[M][20],len;
char s[M],S[N],T[N];
inline void suffixArray(){
    int n=len;
    int m=300,p=0;
    for(int i=1;i<=n;++i) cnt[rk[i]=s[i]]++;
    for(int i=1;i<=m;++i) cnt[i]+=cnt[i-1];
    for(int i=n;i>=1;--i) sa[cnt[rk[i]]--]=i;
    for(int  w=1;p^n;w<<=1,m=p){
        memset(cnt,0,sizeof(cnt)),p=0;
        for(int i=n;i>n-w;--i) id[++p]=i;
        for(int i=1;i<=n;++i) if(sa[i]>w) id[++p]=sa[i]-w;
        for(int i=1;i<=n;++i) cnt[rk[i]]++;
        for(int i=1;i<=m;++i) cnt[i]+=cnt[i-1];
        for(int i=n;i>=1;--i) sa[cnt[rk[id[i]]]--]=id[i];
        memcpy(ork,rk,sizeof(ork)),p=0;
        for(int i=1;i<=n;++i)
            rk[sa[i]]=(ork[sa[i]]==ork[sa[i-1]]&&ork[sa[i]+w]==ork[sa[i-1]+w])?p:++p;
    }
}
inline void getHeight(){
    int n=len;
    for(int i=1,k=0;i<=n;++i){
        if(k) k--;
        while(s[i+k]==s[sa[rk[i]-1]+k]) k++;
        height[rk[i]]=k;
    }
}
int n;
inline int queryMin(int x,int y){
    if(x>y) swap(x,y);
    int k=__lg(y-x+1);
    return min(st[x][k],st[y-(1<<k)+1][k]);
}
inline int querySS(int x,int y){
    x=rk[x],y=rk[y];
    if(x>y) swap(x,y);
    return queryMin(x+1,y);
}
inline int queryTT(int x,int y){
    x=rk[x+2*n+2],y=rk[y+2*n+2];
    if(x>y) swap(x,y);
    return queryMin(x+1,y);
}
inline int queryST(int x,int y){
    x=rk[x],y=rk[y+2*n+2];
    if(x>y) swap(x,y);
    return queryMin(x+1,y);
}
inline int querySSR(int x,int y){
    x=rk[n+1+n-x+1],y=rk[n+1+n-y+1];
    if(x>y) swap(x,y);
    return queryMin(x+1,y);
}
inline int queryTTR(int x,int y){
    x=rk[3*n+3+n-x+1],y=rk[3*n+3+n-y+1];
    if(x>y) swap(x,y);
    return queryMin(x+1,y);
}
inline int querySTR(int x,int y){
    x=rk[n+1+n-x+1],y=rk[3*n+3+n-y+1];
    if(x>y) swap(x,y);
    return queryMin(x+1,y);
}
inline void work(){
    memset(cnt,0,sizeof(cnt));
    memset(id,0,sizeof(id));
    memset(rk,0,sizeof(rk));
    memset(ork,0,sizeof(ork));
    memset(sa,0,sizeof(sa));
    memset(height,0,sizeof(height));
    for(int i=1;i<=n;++i){
        s[i]=S[i];
        s[i+n+1]=S[n-i+1];
        s[i+2*n+2]=T[i];
        s[i+3*n+3]=T[n-i+1];
    }
    s[n+1]='*';
    s[2*n+2]='#';
    s[3*n+3]='@';
    len=4*n+3;
    suffixArray(),getHeight();
    for(int i=1;i<=len;++i) st[i][0]=height[i];
    for(int j=1;j<20;++j){
        for(int i=1;i+(1<<j)-1<=len;++i){
            st[i][j]=min(st[i][j-1],st[i+(1<<j-1)][j-1]);
        }
    }
    for(int l=n;l>=1;--l){
        for(int i=l;i+l<=n;i+=l){
            int j=i+l;
            if(T[i]==T[j]){
                int R=queryTT(i,j)-1;
                int L=queryTTR(i,j)-1;
                int tmp=L+R+querySTR(i-L-1,j-L-1);
                if(tmp>=j-i-1){
                    ans=max(ans,l);
                    return;
                }
            }
            if(S[i]==T[j]){
                int L=querySTR(i,j)-1;
                int R=queryST(i,j)-1;
                int tmp=L+R+queryTT(i+R+1,j+R+1);
                if(tmp>=j-i-1){
                    ans=max(ans,l);
                    return;
                }
            }
        }
    }
}
signed main(){
    n=read();
    scanf("%s%s",S+1,T+2);
	n++;
	S[n]='.';
	T[1]=',';
    work();
    reverse(S+1,S+n+1);
    reverse(T+1,T+n+1);
    swap(S,T);
    work();
    cout<<ans*2;
	return 0;
}