#include <bits/stdc++.h>
#define int long long 
#define ull unsigned long long 
using namespace std;
const int INF=2e5+5;
const int base=233;
int n,ans;
string s1,s2,s3,s4;
ull ba[INF];
struct Ha{
    ull hash1[INF];
    void init(string x) {for (int i=1;i<=n;i++) hash1[i]=hash1[i-1]*base+x[i];}
    ull Get(int l,int r) {return hash1[r]-hash1[l-1]*ba[r-l+1];}
}T1,T3;
int query() {
    s3=s1;s4=s2;
    T1.init(s1);
    for (int l=1,r=n;l<=r;l++,r--) 
        swap(s3[l],s3[r]);
    T3.init(s3);
    int res=0;
    for (int i=1;i<=n;i++) {
        int len=0;
        int l=1,r=min(i,n-i+1),ans=0;
        while (l<=r) {
            int Mid=(l+r)>>1;
            if (T1.Get(i-Mid+1,i+Mid-1)==T3.Get(n-(i+Mid-1)+1,n-(i-Mid+1)+1)) l=(ans=Mid)+1;
            else r=Mid-1;
        }
        len=ans;
        // int len=0;
        // while (i+len<=n && i-len>=1 && s1[i-len]==s1[i+len]) len++;
        if (i-len>=1 && i+len<=n) {
            while (i+len-1<=n && i-len>=1 && s1[i-len]==s2[i+len-1]) len++; 
        }
        res=max(res,len*2-1);
        if (res==n+1) break;
    }
    for (int i=1;i<=n;i++) {
        int len=0;
        int l=1,r=min(i,n-i),ans=0;
        while (l<=r) {
            int Mid=(l+r)>>1;
            if (T1.Get(i-Mid+1,i+Mid)==T3.Get(n-(i+Mid)+1,n-(i-Mid+1)+1)) l=(ans=Mid)+1;
            else r=Mid-1;
        }
        len=ans;
        // while (i+len+1<=n && i-len>=1 && s1[i-len]==s1[i+len+1]) len++;
        // cerr<<len<<" "<<i-3+1<<" "<<i+3<<" "<<n-(i+3)+1<<" "<<n-(i-3+1)+1<<" "<<T1.Get(i-3+1,i+3)<<" "<<T3.Get(n-(i+3)+1,n-(i-3+1)+1)<<" qweorij\n";
        if (i-len>=1 && i+len+1<=n) {
            while (i+len<=n && i-len>=1 && s1[i-len]==s2[i+len]) len++;
        }
        res=max(res,len*2);
        if (res==n+1) break;
    }
    return res;
}
signed main()
{
    ios::sync_with_stdio(false);
    ba[0]=1;
    for (int w=1;w<=2e5;w++) 
        ba[w]=ba[w-1]*base;
    cin>>n>>s1>>s2;
    s1=" "+s1;s2=" "+s2;
    ans=max(ans,query());
    swap(s1,s2);
    for (int l=1,r=n;l<=r;l++,r--) swap(s1[l],s1[r]);
    for (int l=1,r=n;l<=r;l++,r--) swap(s2[l],s2[r]);
    ans=max(ans,query());
    cout<<ans<<"\n";
    return 0;
}