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

// #define int long long
#define fir first
#define sec second
#define mkp make_pair 
#define pb push_back
#define lep( i, l, r ) for ( int i = ( l ); i <= ( r ); ++ i )
#define rep( i, r, l ) for ( int i = ( r ); i >= ( l ); -- i )
 
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef pair < int, int > pii;
 
char _c; bool _f; template < class type > inline void read ( type &x ) {
	_f = 0, x = 0;
	while ( _c = getchar (), !isdigit ( _c ) ) if ( _c == '-' ) _f = 1;
	while ( isdigit ( _c ) ) x = x * 10 + _c - '0', _c = getchar (); if ( _f ) { x = -x; }
}
 
template < class type > inline void chkmin ( type &x, type y ) { x = ( x <= y ? x : y ); }
template < class type > inline void chkmax ( type &x, type y ) { x = ( x >= y ? x : y ); }

const int N = 1e5 + 5;
const int B = 13331;

int n, ans;
ull hsh[N], hsh2[N], pw[N], hsh3[N], hsh4[N];
string s, t;

ull query1 ( int l, int r ) {
  return hsh[r] - hsh[l - 1] * pw[r - l + 1];
}

ull query2 ( int l, int r ) {
  return hsh2[l] - hsh2[r + 1] * pw[r - l + 1];
}

ull query3 ( int l, int r ) {
  return hsh3[r] - hsh3[l - 1] * pw[r - l + 1];
}

ull query4 ( int l, int r ) {
  return hsh4[l] - hsh4[r + 1] * pw[r - l + 1];
}

void init () {
  pw[0] = 1;
  for ( int i = 1; i <= n; i ++ ) {
    pw[i] = pw[i - 1] * B;
  }
}

void calc1 () {
  for ( int i = 1; i <= n; i ++ ) {
    hsh[i] = hsh[i - 1] * B + s[i];
  }
  for ( int i = n; i >= 1; i -- ) {
    hsh2[i] = hsh2[i + 1] * B + s[i];
  }
  for ( int i = 1; i <= n; i ++ ) {
    hsh3[i] = hsh3[i - 1] * B + t[i];
  }
  for ( int i = n; i >= 1; i -- ) {
    hsh4[i] = hsh4[i + 1] * B + t[i];
  }
  // case 1
  for ( int i = 1; i <= n; i ++ ) {
    int l = 1, r = min ( i, n - i + 1 ) + 1;
    while ( l + 1 < r ) {
      int mid = l + r >> 1;
      if ( query1 ( i - mid + 1, i + mid - 1 ) == query2 ( i - mid + 1, i + mid - 1 ) ) {
        l = mid;
      }
      else {
        r = mid;
      }
    }
    int L = 0, R = min ( i - l, n - ( i + l - 1 ) + 1 ) + 1;
    while ( L + 1 < R ) {
      int mid = L + R >> 1;
      if ( query1 ( i - l - mid + 1, i - l ) == query4 ( i + l - 1, i + l - 1 + mid - 1 ) ) {
        L = mid;
      }
      else {
        R = mid;
      }
    }
    ans = max ( ans, 2 * ( l + L ) - 1 );
  }
  // case 2
  for ( int i = 1; i <= n; i ++ ) {
    if ( s[i] == t[i] ) {
      int l = 1, r = min ( i, n - i + 1 ) + 1;
      while ( l + 1 < r ) {
        int mid = l + r >> 1;
        if ( query1 ( i - mid + 1, i ) == query4 ( i, i + mid - 1 ) ) {
          l = mid;
        }
        else {
          r = mid;
        }
      }
      ans = max ( ans, 2 * l );
    }
  }
  // case 3
  for ( int i = 1; i < n; i ++ ) {
    if ( s[i] == s[i + 1] ) {
      int l = 1, r = min ( i, n - i ) + 1;
      while ( l + 1 < r ) {
        int mid = l + r >> 1;
        if ( query1 ( i - mid + 1, i + mid ) == query2 ( i - mid + 1, i + mid ) ) {
          l = mid;
        }
        else {
          r = mid;
        }
      }
      int L = 0, R = min ( i - l, n - ( i + l ) + 1 );
      while ( L + 1 < R ) {
        int mid = L + R >> 1;
        if ( query1 ( i - l - mid + 1, i - l ) == query4 ( i + l, i + l + mid - 1 ) ) {
          L = mid;
        }
        else {
          R = mid;
        }
      }
      ans = max ( ans, 2 * ( l + L ) );
    }
  }
}

void Solve () {
  ios :: sync_with_stdio ( false );
  cin.tie ( 0 ), cout.tie ( 0 );
  cin >> n;
  cin >> s >> t;
  s = " " + s, t = " " + t;
  init ();
  calc1 ();
  reverse ( s.begin (), s.end () );
  reverse ( t.begin (), t.end () );
  swap ( s, t );
  s = " " + s, t = " " + t;
  calc1 ();
  cout << ans;
}

signed main () {
#ifdef judge
	freopen ( "Code.in", "r", stdin );
	freopen ( "Code.out", "w", stdout );
	freopen ( "Code.err", "w", stderr );
#endif
	Solve ();
	return 0;
}