#include <bits/stdc++.h>
#define F first
#define S second
#define ent '\n'
#define int long long
#define pb push_back
typedef long double ld;
typedef long long ll;
using namespace std;
const int maxn = 1e6+12;
const int T = 0;
const int mod = 1e9+7;
int n,m,k,x,y,l,r;
int p[maxn],pref[maxn],fact[maxn];
void solve(){
cin>>n;
int a[n+2],b[n+2];
int cnt=0;
vector<pair<int,int>>v;
for(int i=1;i<=n;i++){
cin>>a[i]>>b[i];
if(b[i]==1)cnt++;
v.pb({b[i],a[i]});
}
if(cnt==n){
cout<<n;
return;
}
// abs(x[i] - x[j]) <= abs(y[i] - y[j]);
int ans=0;
map<int,int>mp;
sort(v.begin(),v.end());
for(int i=v.size()-1;i>=0;i--){
if(!mp[i]){
ans++;
for(int j=i-1;j>=0;j--){
if((v[i].F - v[j].F) >= abs(v[i].S - v[j].S))mp[j]=1;
}
}
}
cout<<ans;
}
//BEKSULTAN TOP
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int t=1;
if(T)cin>>t;
while(t--)solve();
}
