#include<bits/stdc++.h>
using namespace std;

template <typename T>
inline void read(T &x){
	scanf("%d",&x);
//	x = 0;
//	static char c;
//	static bool f;
//	c = getchar(), f = 0;
//	while(c < '0' || c > '9'){ if(c == '-')f = 1; c = getchar(); }
//	while('0' <= c && c <= '9')x = (x << 3) + (x << 1) + (c ^ 48), c = getchar();
//	x = f ? -x : x;
}
template <typename T,typename ...Types>
inline void read(T &x,Types &...y){
	read(x),read(y...);
}

const int N = 1e5 + 10;
const int bas = 1357;
using ll = long long;
using pii = pair<long,long>;
using pi  = pair<int,int>;
int n;
char s[N],t[N];
pii pw[N],S[N],T[N];
pii mod = {1000000007,998244353};
int p1[N],p2[N],ans;
vector<pi> deal;


inline void add(pii &hsh,const pii &pre,char c = '\0'){
	hsh.first = (pre.first * bas % mod.first + c) % mod.first;
	hsh.second = (pre.second * bas % mod.second + c) % mod.second;
}
inline pii getS(int l,int r){
	return { (S[r].first - S[l-1].first * pw[r-l+1].first % mod.first + mod.first) % mod.first,
	         (S[r].second - S[l-1].second * pw[r-l+1].second % mod.second + mod.second) % mod.second };
}
inline pii getT(int l,int r){
	return { (T[l].first - T[r+1].first * pw[r-l+1].first % mod.first + mod.first) % mod.first,
	         (T[l].second - T[r+1].second * pw[r-l+1].second % mod.second + mod.second) % mod.second };
}

inline int LCP(int up,int dn){
	if(up < 1 || dn > n)return 0;
//	cerr << "up=" << up << ",dn=" << dn << ",";
	int l = 1, r = min(up,n-dn+1), res = 0;
	while(l <= r){
		int mid = (l + r) >> 1;
		if(getS(up-mid+1,up) == getT(dn,dn+mid-1)){
			res = mid;
			l = mid+1;
		}else r = mid-1;
	}
//	cerr << "res=" << res << endl;
	return res;
}

char str[N << 1];
void Manacher(char *s,int *p){
	
	int tot = 0;
	str[++tot] = '?';
	str[++tot] = '#';
	for(int i = 1;i<=n;++i){
		str[++tot] = s[i];
		str[++tot] = '#';
	}
	str[++tot] = '!';
	
	for(int i = 1, C = 1, R = 1;i <= tot;++i){
		p[i] = min(p[2*C-i],R-i+1);
		while(str[i-p[i]] == str[i+p[i]])++p[i];
		if(R < i + p[i] - 1)
			R = i + p[i] - 1, C = i;
	}
	/*
	  1 2
	##a#a#
	123456
	*/
	for(int i = 3;i<=tot-2;++i){
		if(str[i] == '#'){
			int len = (p[i] - 1) >> 1;
			if(!len)continue;
			int l = (i >> 1) - len;
			int r = (i >> 1) + len - 1;
			deal.push_back({l,r});
		}else{
			int len = (p[i] >> 1);
			int l = (i >> 1) - len + 1;
			int r = (i >> 1) + len - 1;
			deal.push_back({l,r});
		}
	}
	
}




int main(){
	read(n); scanf("%s%s",s+1,t+1);
	pw[0] = {1,1};
	for(int i = 1;i<=n;++i)
		add(S[i],S[i-1],s[i]),add(pw[i],pw[i-1]);
	for(int i = n;i;--i)
		add(T[i],T[i+1],t[i]);
	Manacher(s,p1);
	for(pi cur : deal){
		int l = cur.first, r = cur.second;
//		printf("l=%d,r=%d,r-l+1=%d,LCP=%d\n",l,r,r-l+1,LCP(l-1,r));
		ans = max(ans,r-l+1+LCP(l-1,r)*2);
	}
	deal.clear();
	Manacher(t,p2);
	for(pi cur : deal){
		int l = cur.first, r = cur.second;
//		printf("l=%d,r=%d,r-l+1=%d,LCP=%d\n",l,r,r-l+1,LCP(l,r+1));
		ans = max(ans,r-l+1+LCP(l,r+1)*2);
	}
	for(int i = 1;i<=n;++i)if(s[i] == t[i]){
		ans = max(ans,2 + LCP(i-1,i+1)*2);
	}
	printf("%d",ans);
	return 0;
}