#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<int> a(n);

  REP (i, n) cin >> a[i];

  int ret = 0;
  REP (i, 2) {
    int tmp = 0;
    int j = i;
    while (j < n) {
      int k = j;
      while (k < n && a[k] == a[j])
        ++k;
      tmp += k - j;
      j = k;
      ++j;  // skip
    }
    ret = max(ret, tmp);
  }
  
  cout << ret << endl;
  
  return 0;
}