#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
const ll LOG = 31;
const ll MOD = 1000000007;
const ll inf = 1e17;
const ll B = 2305843009213693951;
#define f first
#define s second
#define db(x) cerr << #x << " = " << x << " | "
#define dbg(x) cerr << #x << " = " << x << "\n"
#define Algerian ios::sync_with_stdio(0);
#define OI cin.tie(NULL);
int main() {
Algerian OI
// freopen("s.in", "r", stdin);
// freopen("correct.txt", "w", stdout);
ll n;
cin >> n;
vector<pll> a(n + 1);
for (ll i = 1; i <= n; i++) {
cin >> a[i].f >> a[i].s;
a[i].f = min(a[i].f, i - 1);
a[i].s = min(a[i].s, n - i);
}
vector<vector<ll>> dp(n + 1, vector<ll>(2));
for (ll i = 1; i <= n; i++) {
dp[i][0] = max(dp[i - 1][1], dp[i - 1][0]);
for (ll j = 0; j < i - a[i].f; j++) {
if (j + a[j].s < i) dp[i][1] = max(dp[i][1], dp[j][1] + 1);
}
}
cout << max(dp[n][0], dp[n][1]) << "\n";
return 0;
}
