Cairo

#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF (1<<29)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define REP(i, n) FOR(i, 0, n)
#define F(n) REP(i, n)
#define FF(n) REP(j, n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MX (1030)
int T[MX][MX],D;
void ud(int n,int x,int y,int v) {
    while(x<=n){
        int Y=y;
        while(Y<=n)T[x][Y]=max(v,T[x][Y]),Y+=Y&-Y;
        x+=x&-x;
    }
}
int SUM(int x, int y) {
    int S=0;
    while(x>0){
        int Y=y;
        while(Y>0)S=max(S,T[x][Y]),Y-=Y&-Y;
        x-=x&-x;
    }
    return S;
}
int sum(int X,int Y){return SUM(X+1,Y+1);}
void st(int x,int y,int v){ud(D,x+1,y+1,v);}
void ini(int N){D=N,CL(T,0);}
int N,X,Y,S,B;
int main(void){
    scanf("%d",&N),ini(MX-2);
    F(N){
        scanf("%d%d",&X,&Y);
        B=max(B,S=1+sum(X,Y));
        st(X,Y,S);
    }
    printf("%d\n",B);
    return 0;
}