#include <bits/stdc++.h>
using namespace std;
#define print(l) for(auto i:l) cout<<i<<" ";cout<<endl;
#define input(t,l,n) vector<t>l(n);for(int i = 0;i<n;i++)cin>>l[i];
#define int long long
#define pb push_back
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define all(l) l.begin(),l.end()
#define pii pair<int,int>
#define fi first
#define se second
const int M = 1e9+7;
const int inf = 1e18;
void io(){
#ifndef ONLINE_JUDGE
freopen("input.txt","r",stdin);
// freopen("outputf.in","w",stdout);
#endif
}
int bp(int x, int y, int p){
int res = 1;
x = x % p;
while (y > 0) {
if (y & 1)
res = (res * x) % p;
y = y >> 1;
x = (x * x) % p;
}
return res;
}
int MI(int n, int p){
return bp(n, p - 2, p);
}
int mul(int x,int y, int p){
return x * 1ull * y % p;
}
int di(int x,int y, int p){
return mul(x, MI(y, p), p);
}
map<int , vector<int>>adj;
map<int,int>give;
int n , m , k , q;
map<int,int>po;
map<int,int>inde;
map<int,int>outde;
void solve(int testcase_number){
cin>>n;
set<vector<int>>inp;
for(int i = 0;i<n;i++){
cin>>m>>k;
inp.insert({m,m+k,m-k});
inde[m] = 0;
}
map<pair<int,int>,bool>ised;
for(auto i:inp){
// print(i);
for(auto j:inp){
if(i == j)continue;
// print(i);
// print(j);
if(i[0] > j[0] and !ised[{i[0],j[1]}]){
if(i[2]<=j[2]){
ised[{i[0],j[1]}] = 1;
adj[i[0]].pb(j[0]);
inde[j[0]]++;
outde[i[0]]++;
// cout<<(i[2]>=j[2])<<i[2]<<" "<<j[2]<<" "<<i[0]<<" "<<j[0]<<endl;
// cout<<i[0]<<" "<<j[0]<<endl;
}
}
else if(i[0]<j[0] and !ised[{i[0],j[1]}]){
if(i[1]>=j[1]){
ised[{i[0],j[1]}] = 1;
adj[i[0]].pb(j[0]);
inde[j[0]]++;
outde[i[0]]++;
// cout<<i[1]<<" "<<j[1]<<" "<<i[0]<<" "<<j[0]<<endl;
// cout<<i[0]<<" "<<j[0]<<endl;
}
}
}
}
int ans = 0;
for(auto i:inde){
// cout<<i.fi<<" "<<i.se<<endl;
if(i.se == 0){
ans++;
}
}
cout<<ans<<endl;
// for(auto i:adj){
// // print(i.se);
// for(int j:i.se){
// cout<<i.fi<<" "<<j<<endl;
// }
// }
// map<int,int>give;
// }
// for(auto i:inde){
// }
}
signed main(){
// io();
ios::sync_with_stdio(0);//DO NOT USE IN INTERACTIVE
cin.tie(0), cout.tie(0);
cout << fixed<<setprecision(9);
int t = 1;
// cin>>t;
for(int i = 1;i<=t;i++){
solve(i);
}
}
