// A
#include <cstdio>
#include <iostream>
#define ll unsigned long long
#define rep(i, s, t) for(int i=s; i<=t; ++i)
#define debug(x) cerr<<#x<<":"<<x<<endl;
const int N=100010, B=131;
using namespace std;

int n, res; char a[2][N]; ll pw[N], h[2][2][N];
ll H0(ll h[2][N], int l, int r)
{
    return h[0][r]-h[0][l-1]*pw[r-l+1];
}
ll H1(ll h[2][N], int l, int r)
{
    return h[1][l]-h[1][r+1]*pw[r-l+1];
}

int main()
{
#ifdef Jerrywang
    freopen("in.txt", "r", stdin);
#endif
    scanf("%d%s%s", &n, &a[0][1], &a[1][1]);
    pw[0]=1; rep(i, 1, n) pw[i]=pw[i-1]*B;
    rep(k, 0, 1)
    {
        rep(i, 1, n) h[k][0][i]=h[k][0][i-1]*B+a[k][i];
        for(int i=n; i; i--) h[k][1][i]=h[k][1][i+1]*B+a[k][i];
    }
    rep(k, 0, 1) rep(i, 1, n)
    {
        int l=1, r=n, res1=0, res2=0;
        while(l<=r)
        {
            int mid=l+r>>1;
            if(i+mid<=n && i-mid>=1 && H0(h[k], i, i+mid)==H1(h[k], i-mid, i))
                res1=mid, l=mid+1;
            else r=mid-1;
        }
        int l1=i-res1, r1=i+res1;
        l=1, r=n;
        while(l<=r)
        {
            int mid=l+r>>1;
            if(k==0 && l1-mid>=1 && r1+mid-1<=n && H1(h[k], l1-mid, l1-1)==H0(h[k^1], r1, r1+mid-1)
            || k==1 && l1-mid+1>=1 && r1+mid<=n && H1(h[k^1], l1-mid+1, l1)==H0(h[k], r1+1, r1+mid))
                res2=mid, l=mid+1;
            else r=mid-1;
        }
        res=max(res, res1*2+1+res2*2);
        
        l=1, r=n, res1=0, res2=0;
        while(l<=r)
        {
            int mid=l+r>>1;
            if(i+mid-1<=n && i-mid>=1 && H0(h[k], i, i+mid-1)==H1(h[k], i-mid, i-1))
                res1=mid, l=mid+1;
            else r=mid-1;
        }
        l1=i-res1, r1=i+res1-1;
        l=1, r=n;
        while(l<=r)
        {
            int mid=l+r>>1;
            if(k==0 && l1-mid>=1 && r1+mid-1<=n && H1(h[k], l1-mid, l1-1)==H0(h[k^1], r1, r1+mid-1)
            || k==1 && l1-mid+1>=1 && r1+mid<=n && H1(h[k^1], l1-mid+1, l1)==H0(h[k], r1+1, r1+mid))
                res2=mid, l=mid+1;
            else r=mid-1;
        }
        res=max(res, res1*2+res2*2);
    }
    printf("%d", res);

    return 0;
}