#include<bits/stdc++.h>
#define int long long
#define ull unsigned long long
#define repe(i,l,r) for(int (i)=l;(i)<=r;(i)++)
#define rep(i,n) for(int (i)=1;(i)<=n;(i)++)
#define FOR(i,r,l) for(int (i)=r;(i)>=l;(i)--)
#define INF 0x3f3f3f
#define pii pair<int,int>
#define mpr make_pair
#define pb push_back
#define ALL(v) (v).begin(),(v).end()
#define rsort(v) sort(ALL(v),greater<int>())
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
using namespace std;
int read(){int sum=0,f=1;char c;c=getchar();while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}while(c>='0'&&c<='9'){sum=(sum<<1)+(sum<<3)+(c-'0');c=getchar();}return sum*f;}
void out(int x){if(x<0){x=-x;putchar('-');}if(x>=10)out(x/10);putchar(x%10+'0');}
template <typename T>void die(T s){cout<<s<<endl;exit(0);}
int fast(int a,int b,int P){int res=1;if(P<=0){while(b){if(b&1)res=res*a;a=a*a;b>>=1;}}else{while(b){if(b&1)res=res*a%P;a=a*a%P;b>>=1;}}return res;}
template <typename T>void chkmax(T& a,T b){if(a<b)a=b;return;}
template <typename T>void chkmin(T& a,T b){if(a>b)a=b;return;}
int n;
const int N=1e5+5,base=1441,P=998244353;
char s[2][N];
int hs[2][2][N];
int pw[N];
int get_hash(int o,int p,int l,int r){
    if(!o){
        return (hs[o][p][r]-hs[o][p][l-1]*pw[r-l+1]%P+P)%P;
    }
    else{
        return (hs[o][p][l]-hs[o][p][r+1]*pw[r-l+1]%P+P)%P;
    }
}
int calc(int a,int b,int c,int d){
    if(!b||d==n+1)return 0;
    int l=1,r=min(b,n-d+1),ans=0;
    while(l<=r){
        int mid=l+r>>1;
        if(get_hash(1,a,b-mid+1,b)==get_hash(0,c,d,d+mid-1))l=mid+1,ans=mid;
        else r=mid-1;
    }
    return ans;
}
signed main(){
    n=read();
    scanf("%s %s",s[0]+1,s[1]+1);
    pw[0]=1;
    for(int i=1;i<=n;i++)pw[i]=pw[i-1]*base%P;
    for(int i=0;i<2;i++){
        for(int j=1;j<=n;j++){
            //cerr<<i<<' '<<j<<endl;
            hs[0][i][j]=(hs[0][i][j-1]*base%P+s[i][j])%P;
        }
    }
    for(int i=0;i<2;i++){
        for(int j=n;j>=1;j--){
            hs[1][i][j]=(hs[1][i][j+1]*base%P+s[i][j])%P;
        }
    }
    int ans=0;
    for(int p=0;p<2;p++){
        for(int i=1;i<=n;i++){
            int len1=calc(p,i,p,i),len2;
            if(!p){
                len2=calc(p,i-len1,1,i+len1-1);
            }
            else{
                len2=calc(0,i-len1+1,1,i+len1);
            }
            chkmax(ans,len1*2-1+len2*2);
        }
    }
    //cerr<<hs[0][1][1]<<' '<<hs[0][1][2]<<' '<<hs[0][1][3]<<' '<<s[1][1]<<endl;
    // cout<<get_hash(1,0,1,3)<<' '<<get_hash(0,1,3,5)<<' '<<hs[0][1][3]<<endl;
    //cout<<ans<<endl;
    for(int p=0;p<2;p++){
        for(int i=1;i<=n;i++){
            if(i>1){
                int len1=calc(p,i-1,p,i),len2;
                if(!p){
                    len2=calc(p,i-1-len1,1,i+len1-1);
                }
                else{
                    len2=calc(0,i-len1,1,i+len1);
                }
                chkmax(ans,len1*2+len2*2);
            }
            if(p){
                int len1=calc(0,i,p,i);
                chkmax(ans,len1*2);
            }
        }
    }
    out(ans);
    return 0;
}