//vanitas vanitatum et omnia vanitas
#include<bits/stdc++.h>
#define fi first
#define se second
#define eb emplace_back
#define mp make_pair
using namespace std;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
template<typename T,typename U>
T ceil(T x, U y) {return (x>0?(x+y-1)/y:x/y);}
template<typename T,typename U>
T floor(T x, U y) {return (x>0?x/y:(x-y+1)/y);}
template<class T,class S>
bool chmax(T &a,const S b) {return (a<b?a=b,1:0);}
template<class T,class S>
bool chmin(T &a,const S b) {return (a>b?a=b,1:0);}
int popcnt(int x) {return __builtin_popcount(x);}
int popcnt(ll x)  {return __builtin_popcountll(x);}
int topbit(int x) {return (x==0?-1:31-__builtin_clz(x));}
int topbit(ll x)  {return (x==0?-1:63-__builtin_clzll(x));}
int lowbit(int x) {return (x==0?-1:__builtin_ctz(x));}
int lowbit(ll x)  {return (x==0?-1:__builtin_ctzll(x));}

#define int long long
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pii> vp;
typedef tuple<int,int,int> tiii;
int read() {
  int x=0,w=1; char c=getchar(); 
  while(!isdigit(c)) {if(c=='-') w=-1; c=getchar();}
  while(isdigit(c)) {x=x*10+(c-'0'); c=getchar();}
  return x*w;
}

const int N=5e5+5;
int n,a[N],b[N],ans;
vi p[N];

void work(int *a) {
  static int st[N]; int top=0;
  rep(i,2,n) ans+=(a[i]!=a[i-1]);
  rep(i,1,n) {
    while(top&&a[st[top]]>a[i]) --top;
    if(a[st[top]]==a[i]) {
      if(st[top]!=i-1) p[st[top]+1].eb(i), --ans;
      st[top]=i;
    } else st[++top]=i;
  }
}

signed main() {
  n=read();
  rep(i,1,n) a[i]=read(), b[i]=read();
  work(a), work(b);
  int X=1; priority_queue<int,vi,greater<int>> q;
  rep(i,2,n) if(a[i]!=a[i-1]&&b[i]!=b[i-1]) {
    --ans;
    while(X<i) {++X; for(int r:p[X]) q.push(r);}
    while(!q.empty()&&q.top()<i) q.pop();
    if(!q.empty()) q.pop(), ++ans;
  } 
  printf("%lld\n",ans);
  return 0;
}