#include<bits/stdc++.h>
using namespace std;
#define read(st,en,a) for(int II=st;II<=en;II++) cin>>a[II]
#define up(s,e,i) for(int i=s;i<=e;i++)
#define down(s,e,i) for(int i=s;i>=e;i--) 
#define all(x) x.begin(),x.end()
#define endl '\n' 

namespace Main
{
    const int N = 100010;
    int n;
    string s, t;
    int match(int x,int y)
    {
        if(x<0||y>=n)
            return 0;
        int res = 0;
        while(1)
        {
            if(s[x]!=t[y])
                return res;
            res++;
            x--, y++;
            if(x<0||y>=n)
                return res;
        }
        return 114514;
    }
    int x[N * 2];
    string get(string s)
    {
        string res;
        res += "`#";
        for(auto i:s)
            res += i, res += "#";
        res += " ";
        return res;
    }

    void main()
    {
        ios::sync_with_stdio(0);
        cin.tie(0);cout.tie(0);
        
        cin >> n >> s >> t;
        int ans = 0;
        up(0, n - 1, i) ans = max(ans, match(i, i)*2);

        int mid = 0, r = 0;
        string str = get(s);
        up(2,str.size()-3,i)
        {
            if(r>i)
                x[i] = min(x[mid * 2 - i], r - i);
            while(str[i+x[i]+1]==str[i-x[i]-1])
                x[i]++;
            if(i+x[i]>r)
                r = i + x[i], mid = i;

            int l = (i - x[i] + 1) / 2 - 1, r = (i + x[i] - 1) / 2 - 1;
            if(l<=r) ans = max(ans, r - l + 1 + match(l - 1, r) * 2);
        }
        mid = 0, r = 0;
        memset(x, 0, sizeof x);
        str = get(t);
        up(2,str.size()-3,i)
        {
            if(r>i)
                x[i] = min(x[mid * 2 - i], r - i);
            while(str[i+x[i]+1]==str[i-x[i]-1])
                x[i]++;
            if(i+x[i]>r)
                r = i + x[i], mid = i;

            int l = (i - x[i] + 1) / 2 - 1, r = (i + x[i] - 1) / 2 - 1;
            if(l<=r) ans = max(ans, r - l + 1 + match(l, r + 1) * 2);
        }
        cout << ans;
    }
};

int main()
{
    Main::main();
    return 0;
}