#include <bits/stdc++.h>
using namespace std;
#include <math.h>
#include <iomanip>
#include <cstdint>
#include <string>
#include <sstream>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
#define rep(i,n) for (int i = 0; i < (n); ++i)
typedef long long ll;
using P = pair<int,int>;
const int INF=1001001001;
const int mod =1e9+7;
int N,L[10005];
vector<int>A;
int lis(){
  L[0]=A[0];
  int length=1;
  for(int i=1;i<N;i++){
    if(L[length-1]<A[i]-1){L[length++]=A[i];}
    else{*lower_bound(L,L+length,A[i]-1)=A[i];}
  }
  return length;
}

int main() {
  cin>>N;
  A.resize(N);
  for(int i=0;i<N;i++){
    cin>>A[i];
  }
  sort(A.begin(),A.end());
  cout<<lis()<<endl;
  return 0;
}