#include <bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("Ofast,fast-math,O3")
#define pb push_back
#define ll long long
#define f first
#define s second
//#define sz(v) int(v.size())
#define all(v) v.begin(),v.end()
int mod = 1e9 + 7;
const int N = 1e7 + 2,k = 317 + 1;
const int inf = 2e9;
int pr = -inf,sf = inf;
bool d[N];
inline int func(){
int x = 0;
int f = 1;
char ch = getchar_unlocked();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar_unlocked();
}
while (ch >= '0' && ch <= '9') {
x = x * 10 + (ch - '0');
ch = getchar_unlocked();
}
return x * f;
}
void solve(){
int n,ans = 0;
n = func();
int x[n + 1],y[n + 1];
int g;
for(int i = 1; i <= n; i++){
x[i] = func(),y[i] = func();
g = x[i] + y[i];
d[i] |= (pr >= g);
pr = max(pr,g);
}
for(int i = n; i >= 1; i--){
g = x[i] - y[i];
d[i] |= (sf <= g);
sf = min(sf,g);
ans += (d[i] == 0);
}
cout << ans;
}
signed main(){
//freopen("time.in", "r", stdin);
//freopen("time.out", "w", stdout);
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
int t = 1;
while(t--){
solve();
}
}
