1 #pragma GCC optimize("Ofast")
2 #include <bits/stdc++.h>
3 #define maxn 13003
4 #define _for(i,a,b) for(int i = (a);i < b;i ++)
5 typedef long long ll;
6 using namespace std;
7
8 inline ll read()
9 {
10 ll ans = 0;
11 char ch = getchar(), last = ' ';
12 while(!isdigit(ch)) last = ch, ch = getchar();
13 while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
14 if(last == '-') ans = -ans;
15 return ans;
16 }
17 inline void write(ll x)
18 {
19 if(x < 0) x = -x, putchar('-');
20 if(x >= 10) write(x / 10);
21 putchar(x % 10 + '0');
22 }
23 struct wood
24 {
25 int W;
26 int L;
27 };
28 int n;
29 wood in[5003];
30 int dp[5003];
31 int dpend = 1;
32 bool cmp(wood a,wood b)
33 {
34 if(a.L == b.L)
35 return a.W > b.W;
36 return a.L > b.L;
37 }
38
39 int main()
40 {
41 n = read();
42 _for(i,1,n+1)
43 {
44 in[i].L = read();
45 in[i].W = read();
46 }
47 sort(in+1,in+n+1,cmp);
48
49 dp[dpend] = in[1].W;
50 _for(i,2,n+1)
51 {
52 if(in[i].W > dp[dpend])
53 dp[++dpend] = in[i].W;
54 else
55 {
56 int t = lower_bound(dp+1,dp+dpend+1,in[i].W)-dp;
57 dp[t] = in[i].W;
58 }
59 }
60 write(dpend);
61 return 0;
62 }
