#include <bits/stdc++.h>
// #include <windows.h>
// #include <bits/extc++.h>
// using namespace __gnu_pbds;
using namespace std;
//#pragma GCC optimize(3)
#define DB double
#define LL long long
#define ULL unsigned long long
#define in128 __int128
#define cint const int
#define cLL const LL
#define For(z,e1,e2) for(int z=(e1);z<=(e2);z++)
#define Rof(z,e1,e2) for(int z=(e2);z>=(e1);z--)
#define For_(z,e1,e2) for(int z=(e1);z<(e2);z++)
#define Rof_(z,e1,e2) for(int z=(e2);z>(e1);z--)
#define inint(e) scanf("%d",&e)
#define inll(e) scanf("%lld",&e)
#define inpr(e1,e2) scanf("%d%d",&e1,&e2)
#define in3(e1,e2,e3) scanf("%d%d%d",&e1,&e2,&e3)
#define outint(e) printf("%d\n",e)
#define outint_(e) printf("%d%c",e," \n"[i==n])
#define outint2_(e,e1,e2) printf("%d%c",e," \n"[(e1)==(e2)])
#define outll(e) printf("%lld\n",e)
#define outll_(e) printf("%lld%c",e," \n"[i==n])
#define outll2_(e,e1,e2) printf("%lld%c",e," \n"[(e1)==(e2)])
#define exc(e) if(e) continue
#define stop(e) if(e) break
#define ret(e) if(e) return
#define ll(e) (1ll*(e))
#define pb push_back
#define ft first
#define sc second
#define pii pair<int,int> 
#define pli pair<long long,int> 
#define vct vector 
#define clean(e) while(!e.empty()) e.pop()
#define all(ev) ev.begin(),ev.end()
#define sz(ev) ((int)ev.size())
#define debug(x) printf("%s=%d\n",#x,x)
#define x0 __xx00__
#define y1 __yy11__
#define ffo fflush(stdout)
// cLL mod=998244353,G=404;
// cLL mod[2]={1686688681ll,1666888681ll},base[2]={166686661ll,188868881ll};
cLL mod=1686688681ll,base=166686661ll;
template <typename Type> void get_min(Type &w1,const Type w2) { if(w2<w1) w1=w2; } template <typename Type> void get_max(Type &w1,const Type w2) { if(w2>w1) w1=w2; }
template <typename Type> Type up_div(Type w1,Type w2) { return (w1/w2+(w1%w2?1:0)); }
template <typename Type> Type gcd(Type X_,Type Y_) { Type R_=X_%Y_; while(R_) { X_=Y_; Y_=R_; R_=X_%Y_; } return Y_; } template <typename Type> Type lcm(Type X_,Type Y_) { return (X_/gcd(X_,Y_)*Y_); }
template <typename Type> Type md(Type w1,const Type w2=mod) { w1%=w2; if(w1<0) w1+=w2; return w1; } template <typename Type> Type md_(Type w1,const Type w2=mod) { w1%=w2; if(w1<=0) w1+=w2; return w1; }
void ex_gcd(LL &X_,LL &Y_,LL A_,LL B_) { if(!B_) { X_=1ll; Y_=0ll; return ; } ex_gcd(Y_,X_,B_,A_%B_); X_=md(X_,B_); Y_=(1ll-X_*A_)/B_; } LL inv(LL A_,LL B_=mod) { LL X_=0ll,Y_=0ll; ex_gcd(X_,Y_,A_,B_); return X_; }
template <typename Type> void add(Type &w1,const Type w2,const Type M_=mod) { w1=md(w1+w2,M_); } void mul(LL &w1,cLL w2,cLL M_=mod) { w1=md(w1*md(w2,M_),M_); } template <typename Type> Type pw(Type X_,Type Y_,Type M_=mod) { Type S_=1; while(Y_) { if(Y_&1) mul(S_,X_,M_); Y_>>=1; mul(X_,X_,M_); } return S_; }
template <typename Type> Type bk(vector <Type> &V_) { auto T_=V_.back(); V_.pop_back(); return T_; } template <typename Type> Type tp(stack <Type> &V_) { auto T_=V_.top(); V_.pop(); return T_; } template <typename Type> Type frt(queue <Type> &V_) { auto T_=V_.front(); V_.pop(); return T_; }
template <typename Type> Type bg(set <Type> &V_) { auto T_=*V_.begin(); V_.erase(V_.begin()); return T_; } template <typename Type> Type bk(set <Type> &V_) { auto T_=*prev(V_.end()); V_.erase(*prev(V_.end())); return T_; }
mt19937 gen(time(NULL)); int rd() { return abs((int)gen()); }
int rnd(int l,int r) { return rd()%(r-l+1)+l; }

void main_init()
{

}
cint N=1.02e5,K=26;
int n;
LL h[K+2];
char s1[N],s2[N];
LL d[N];
LL hs1[N][2],hs2[N][2];
void init(char s[],LL hs[][2])
{
    For(i,1,n) hs[i][0]=(hs[i-1][0]*base+h[s[i]-'a'])%mod;
    Rof(i,1,n) hs[i][1]=(hs[i+1][1]*base+h[s[i]-'a'])%mod;
}
LL ghs(LL hs[][2],int l,int r,int opt)
{
    return md(opt?(hs[l][1]-hs[r+1][1]*d[r-l+1]):(hs[r][0]-hs[l-1][0]*d[r-l+1]));
}
void main_solve()
{
    For(i,0,K+1) h[i]=1ll*rnd(1,(int)mod);
    scanf("%d%s%s",&n,s1+1,s2+2);
    n++;
    s1[n]='{',s2[1]='}';
    init(s1,hs1),init(s2,hs2);
    d[0]=1ll; For(i,1,n) d[i]=d[i-1]*base%mod;
    int ans=0;
    For(round,0,1)
    {
        // printf("round=%d\n",round);
        #define hs (round?hs2:hs1)
        For_(i,1,n)
        {
            auto ck=[&](int k)->bool
            {
                return (ghs(hs,i-k+1,i,0)==ghs(hs,i,i+k-1,1));
            };
            int d;
            auto ck2=[&](int k)->bool
            {
                return (ghs(hs1,i-k+1,i-d,0)==ghs(hs2,i+d,i+k-1,1));
            };
            int l=1,r=min(i,n-i)+1,mid;
            while(l+1<r)
                (ck(mid=l+r>>1)?l:r)=mid;
            d=l,r=min(i,n-i+1)+1;
            // printf("d=%d\n",d);
            // printf("[%d,%d]\n",i-d+1,i+d-1);
            // printf("%d,%d\n",ck2(d),ck2(d+1));
            while(l+1<r)
                (ck2(mid=l+r>>1)?l:r)=mid;
            get_max(ans,(l<<1)-1);
        }
        For_(i,1,n)
        {
            auto ck=[&](int k)->bool
            {
                return (ghs(hs,i-k+1,i,0)==ghs(hs,i+1,i+k,1));
            };
            int d;
            auto ck2=[&](int k)->bool
            {
                return (ghs(hs1,i-k+1,i-d,0)==ghs(hs2,i+d+1,i+k,1));
            };
            int l=0,r=min(i,n-i-1)+1,mid;
            while(l+1<r)
                (ck(mid=l+r>>1)?l:r)=mid;
            d=l,r=min(i,n-i)+1;
            while(l+1<r)
                (ck2(mid=l+r>>1)?l:r)=mid;
            get_max(ans,l<<1);
        }
    }
    outint(ans);
}
int main()
{
    // ios::sync_with_stdio(0); cin.tie(0);
    // freopen("ex_block4.in","r",stdin);
    // freopen("out.txt","w",stdout);
    // srand(time(NULL));
    main_init();
    // int _; inint(_); For(__,1,_) // T>1 ?
        // printf("\n------------\n\n"),
        main_solve();
    // cerr<<clock()<<'\n';
    return 0;
}
/*

*/