#include <bits/stdc++.h>
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx,avx2,fma")
using namespace std;
#define ll int
#define sped_up ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define rall(v) (v).rbegin(), (v).rend()
#define all(v) (v).begin(), (v).end()
#define pb push_back
#define S second
#define F first
const ll INF = (ll)1e9 + 1, INFL = (ll)1e18 + 1;
const ll mod = (ll)1e9 + 7, MAXN = (ll)1e7 + 7;
ll p[MAXN], s[MAXN];
int main() {
sped_up;
ll n;
cin >> n;
ll cnt = 0;
vector <pair <ll, ll>> v;
v.pb({0, 0});
p[0] = -INF;
s[n + 1] = INF;
for (int i = 1; i <= n; i++) {
ll x, y;
cin >> x >> y;
v.pb({x, y});
}
for (int i = 1; i <= n; i++) {
ll x = v[i].F, y = v[i].S;
p[i] = max(p[i - 1], x + y);
}
for (int i = n; i >= 1; i--) {
ll x = v[i].F, y = v[i].S;
s[i] = min(s[i + 1], x - y);
}
for (int i = 1; i <= n; i++) {
ll x = v[i].F, y = v[i].S;
if (s[i + 1] > x - y && x + y > p[i - 1]) cnt++;
}
cout << cnt;
}
