#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
const int MAXN = 5e5 + 10;
void speed()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
}
int n, a[MAXN], b[MAXN];
void read()
{
cin >> n;
for (int i = 1; i <= n; ++ i)
{
cin >> a[i] >> b[i];
}
}
int in[MAXN];
void solve()
{
for (int i = 1; i <= n; ++ i)
{
for (int j = 1; j <= n; ++ j)
{
if(i != j && b[i] >= b[j] && abs(a[i] - a[j]) <= b[i] - b[j])
{
if(a[i] == a[j] && b[i] == b[j] && i > j)continue;
in[j] ++;
}
}
}
int ans = 0;
for (int i = 1; i <= n; ++ i)
if(!in[i])ans ++;
cout << ans << endl;
}
int main()
{
speed();
read();
solve();
return 0;
}
