import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }




void main() {
  try {
    for (; ; ) {
      const N = readInt();
      auto S = new int[N];
      foreach (x; 0 .. N) {
        S[x] = readInt();
      }
      auto T = new int[N];
      foreach (y; 0 .. N) {
        T[y] = readInt();
      }
      
      auto a = new int[][](N, N);
      foreach (x; 0 .. N) foreach (y; 0 .. N) {
        a[x][y] = -1;
      }
      foreach (x; 0 .. N) {
        if (S[x] == 0) foreach (y; 0 .. N) a[x][y] = 0;
        if (S[x] == 2) foreach (y; 0 .. N) a[x][y] = 1;
      }
      foreach (y; 0 .. N) {
        if (T[y] == 0) foreach (x; 0 .. N) a[x][y] = 0;
        if (T[y] == 2) foreach (x; 0 .. N) a[x][y] = 1;
      }
      debug {
        writeln("a = ", a);
      }
      
      int cntX, cntY;
      foreach (x; 0 .. N) {
        if (S[x] == 1) {
          bool has;
          foreach (y; 0 .. N) {
            has = has || (a[x][y] == 1);
          }
          if (!has) {
            ++cntX;
          }
        }
      }
      foreach (y; 0 .. N) {
        if (S[y] == 1) {
          bool has;
          foreach (x; 0 .. N) {
            has = has || (a[x][y] == 1);
          }
          if (!has) {
            ++cntY;
          }
        }
      }
      
      int ans;
      foreach (x; 0 .. N) foreach (y; 0 .. N) {
        if (a[x][y] == 1) {
          ++ans;
        }
      }
      ans += max(cntX, cntY);
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}