#include<bits/stdc++.h>
#define ull unsigned long long
using namespace std;
const int MAXN=1e5+5;
int n,ans=0;
char s[2][MAXN];
ull B,pw[MAXN],hs[2][MAXN],rs[2][MAXN];
ull query(ull *h,int l,int r) { return h[r]-h[l-1]*pw[r-l+1]; }
ull rquery(ull *h,int l,int r) { return query(h,n-r+1,n-l+1); }
bool check(int l,int k,int r) {
	return query(hs[0],l,k)*pw[r-k+1]+query(hs[1],k,r)==rquery(rs[1],k,r)*pw[k-l+1]+rquery(rs[0],l,k);
}
void solve() {
	for(int i=1;i<=n;++i){
        int res1=0,res2=0,l=0,r=min(i-1,n-i);
        while(l<=r){
            int mid=(l+r)>>1;
            if(check(i-mid,i+mid,i+mid-1))res1=mid,l=mid+1;
            else r=mid-1;
        }
        l=0,r=min(i-1-res1,n-i-res1+1);
        while(l<=r){
            int mid=(l+r)>>1;
            if(check(i-res1-mid,i+res1,i+res1+mid-1))res2=mid,l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,2*res1+2*res2+1);
    }
	for(int i=1;i<n;++i)if(s[0][i]==s[0][i+1]){
        int res1=0,res2=0,l=0,r=min(i,n-i);
        while(l<=r){
            int mid=(l+r)>>1;
            if(check(i-mid+1,i+mid,i+mid-1))res1=mid,l=mid+1;
            else r=mid-1;
        }
        l=0,r=min(i-res1,n-i-res1+1);
        while(l<=r){
            int mid=(l+r)>>1;
            if(check(i-res1-mid+1,i+res1,i+mid+res1-1))res2=mid,l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,2*res1+2*res2);
    }
	for(int i=1;i<=n;++i)if(s[0][i]==s[1][i]){
        int res1=0,l=0,r=min(i,n-i+1);
        while(l<=r){
            int mid=(l+r)>>1;
            if(check(i-mid+1,i,i+mid-1))res1=mid,l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,2*res1);
    }
}
signed main() {
	scanf("%d%s%s",&n,s[0]+1,s[1]+1),B=1e9+7;
	for(int i=pw[0]=1;i<=n;++i) pw[i]=pw[i-1]*B;
	for(int o:{0,1}) {
		for(int i=1;i<=n;++i) {
			hs[o][i]=hs[o][i-1]*B+s[o][i]-'a';
			rs[o][i]=rs[o][i-1]*B+s[o][n-i+1]-'a';
		}
	}
	solve();
	swap(s[0],s[1]),swap(hs[0],rs[1]),swap(hs[1],rs[0]);
	reverse(s[0]+1,s[0]+n+1),reverse(s[1]+1,s[1]+n+1);
	solve();
	printf("%d\n",ans);
	return 0;
}