1 #include <iostream>
 2 #include <string>
 3 #include <cstdio>
 4 #include <cstring>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <cmath>
 8 #include <vector>
 9 #include <queue>
10 #include <stack>
11 #include <set>
12 #include <map>
13 using namespace std;
14 typedef long long           LL ;
15 typedef unsigned long long ULL ;
16 const int    maxn = 1e5 + 10   ;
17 const int    inf  = 0x3f3f3f3f ;
18 const int    npos = -1         ;
19 const int    mod  = 1e9 + 7    ;
20 const int    mxx  = 100 + 5    ;
21 const double eps  = 1e-6       ;
22 const double PI   = acos(-1.0) ;
23 
24 struct node{
25     int p, d;
26 };
27 node h[maxn];
28 int cmp(const node &l, const node &r){
29     if(l.p!=r.p)
30         return l.p<r.p;
31     else
32         return l.d<r.d;
33 }
34 int Lower_Bound(int l, int r, int x){
35     while(l<r){
36         int m=(l+r)>>1;
37         if(h[m].p>=x)
38             r=m;
39         else
40             l=m+1;
41     }
42     return l;
43 }
44 int n, u, v, fac[30], st[maxn], cnt;
45 int dp[maxn][30], pl, pr, id;
46 int main(){
47     // freopen("in.txt","r",stdin);
48     // freopen("out.txt","w",stdout);
49     for(int i=0;i<30;i++)
50         fac[i]=(1<<i);
51     while(~scanf("%d",&n)){
52         for(int i=1;i<=n;i++){
53             scanf("%d %d",&h[i].p,&h[i].d);
54             dp[i][0]=i;
55         }
56         sort(h+1,h+1+n,cmp);
57         int k=(int)(log((double)n)/log(2.0));
58         for(int j=1;j<=k;j++)
59             for(int i=1;i+fac[j]-1<=n;i++){
60                 pl=dp[i][j-1];
61                 pr=dp[i+fac[j-1]][j-1];
62                 if(h[pl].d<h[pr].d)
63                     dp[i][j]=pl;
64                 else
65                     dp[i][j]=pr;
66             }
67         u=1;
68         cnt=0;
69         st[cnt++]=1;
70         for(int i=2;i<=n;i++){
71             v=Lower_Bound(1,i,h[i].p)-1;
72             if(u<=v){
73                 k=(int)(log((double)v)/log(2.0));
74                 pl=dp[u][k];
75                 pr=dp[v-fac[k]+1][k];
76                 if(h[pl].d<h[pr].d)
77                     id=pl;
78                 else
79                     id=pr;
80                 if(!(h[id].d<h[i].d))
81                     st[cnt++]=i;
82             }else{
83                 st[cnt++]=i;
84             }
85         }
86         printf("%d\n",cnt);
87         for(int i=0;i<cnt;i++)
88             printf("%d %d\n",h[st[i]].p,h[st[i]].d);
89     }
90     return 0;
91 }