#include<bits/stdc++.h>
 
using namespace std;
 
int n;
int st[1000], en[1000];
int dp[1000][1000];
 
int solve(int index, int currentFinishTime){
	if(index == n) return 0;
	int v1 = 0, v2 = 0;
	if(dp[index][currentFinishTime] != -1) return dp[index][currentFinishTime];
 
	//do not choose the current activity
	v1 = solve(index+1, currentFinishTime);
 
	//try to choose the current activity
	if(st[index] >= currentFinishTime){
		v2 = solve(index+1, en[index]) + 1;
	}
	return dp[index][currentFinishTime] = max(v1, v2);
}
 
int main(){
	cin >> n;
	for(int i = 0;i < n;i++) cin >> st[i] >> en[i];
	memset(dp, -1, sizeof dp);
 
	cout << solve(0, 0) << endl;
return 0;
}
 
/*
11
1 4
3 5
0 6
5 7
3 9
5 9
6 10
8 11
8 12
2 14
12 16
*/

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MTEKMSA0CjMgNQowIDYKNSA3CjMgOQo1IDkKNiAxMAo4IDExCjggMTIKMiAxNAoxMiAxNg==

11
1 4
3 5
0 6
5 7
3 9
5 9
6 10
8 11
8 12
2 14
12 16