#include<stdio.h>
#include<stdlib.h>
#include<algorithm>
#include<vector>
using namespace std;
vector< pair<int, int> > v;

int A[100100];
int main(){
	int i, n, a, b, ans=0, cnt=0;
	scanf("%d", &n);
	for(i=0;i<n;i++){
		scanf("%d %d", &a, &b);
		v.push_back({b,a});
	}

	ans = cnt = 0;
    sort(v.begin(), v.end());

    for(i=0;i<n;i++){
        pair<int, int> k = v[i];
        printf("%d : %d %d\n",i,k.first, k.second);
        if(cnt <= k.second){
            cnt = k.first;
            ans++;
        }
    }

	printf("%d",ans);
}