#include<bits/stdc++.h>
using namespace std;
using ll=long long;
using ld=long double;
using pear=pair<ll, ll>;
#define fi first
#define se second
#define nl << '\n'
#define uk << ' '
void dfs(ll u, ll& ans, vector<vector<ll>>& adj){
ans++;
for(auto v:adj[u]){
dfs(v, ans, adj);
}
return;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
// freopen(".inp","r",stdin);
// freopen(".out","w",stdout);
cin.exceptions(cin.failbit);
ll n;
cin >> n;
ll i, j;
vector<vector<ll>> adj(n+1);
for(i=1; i<=n; i++){
ll d, x;
cin >> d >> x;
if(d==0) continue;
for(j=1; j<=x; j++){
if(i+d*j>n) break;
adj[i].push_back(i+d*j);
}
}
ll ans=0;
dfs(1, ans, adj);
cout << ans;
}
