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

typedef long long ll;
typedef __int128 Int;

const ll maxn=1e5+5, P=998244353, mo=1e18+7;

char s[maxn], t[maxn];

ll f[maxn], g[maxn], pw[maxn];
ll f2[maxn], g2[maxn];

ll calcf(ll l,ll r) {
    return (f[r]-(Int)pw[r-l+1]*f[l-1]%mo+mo)%mo;
}

ll calcf2(ll l,ll r) {
    return (f2[l]-(Int)pw[r-l+1]*f2[r+1]%mo+mo)%mo;
}

ll calcg(ll l,ll r) {
    return (g[r]-(Int)pw[r-l+1]*g[l-1]%mo+mo)%mo;
}

ll calcg2(ll l,ll r) {
    return (g2[l]-(Int)pw[r-l+1]*g2[r+1]%mo+mo)%mo;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    ll n; cin>>n;
    pw[0]=1;
    for(ll i=1;i<=n;i++) pw[i]=(Int)pw[i-1]*P%mo;
    for(ll i=1;i<=n;i++) cin>>s[i];
    for(ll i=1;i<=n;i++) cin>>t[i];
    for(ll i=1;i<=n;i++) f[i]=((Int)f[i-1]*P+s[i]-'a')%mo, g[i]=((Int)g[i-1]*P+t[i]-'a')%mo;
    for(ll i=n;i>=1;i--) f2[i]=((Int)f2[i+1]*P+s[i]-'a')%mo, g2[i]=((Int)g2[i+1]*P+t[i]-'a')%mo;
    ll ans=0;
    for(ll i=1;i<=n;i++) {
        ll l=1, r=min(i,n-i+1), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcf(i-mid+1,i)==calcf2(i,i+mid-1)) len=mid, l=mid+1;
            else r=mid-1;
        }
        ll L=i-len+1, R=i+len-1;
        l=1, r=min(L-1,n-R+1), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcf(L-mid,L-1)==calcg2(R,R+mid-1)) len=mid, l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,len*2+R-L+1);

        l=1, r=min(i,n-i), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcf(i-mid+1,i)==calcf2(i+1,i+mid)) len=mid, l=mid+1;
            else r=mid-1;
        }
        L=i-len+1, R=i+len;
        l=1, r=min(L-1,n-R+1), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcf(L-mid,L-1)==calcg2(R,R+mid-1)) len=mid, l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,len*2+R-L+1);

        l=1, r=min(i,n-i+1), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcg(i-mid+1,i)==calcg2(i,i+mid-1)) len=mid, l=mid+1;
            else r=mid-1;
        }
        L=i-len+1, R=i+len-1;
        l=1, r=min(L,n-R), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcf(L-mid+1,L)==calcg2(R+1,R+mid)) len=mid, l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,len*2+R-L+1);

        l=1, r=min(i,n-i), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcg(i-mid+1,i)==calcg2(i+1,i+mid)) len=mid, l=mid+1;
            else r=mid-1;
        }
        L=i-len+1, R=i+len;
        l=1, r=min(L,n-R), len=0;
        while(l<=r) {
            ll mid=l+r>>1;
            if(calcf(L-mid+1,L)==calcg2(R+1,R+mid)) len=mid, l=mid+1;
            else r=mid-1;
        }
        ans=max(ans,len*2+R-L+1);
    }
    cout<<ans<<'\n';
    return 0;
}