#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pl pair<long, long>
#define pll pair<ll, ll>
#define f first
#define s second
#define MOD 1000000007
ll ress[100005], ds[100005], xs[100005];
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
long N;
cin >> N;
for (long i=1; i<1+N; i++) {
cin >> ds[i] >> xs[i];
}
ll xp, res;
for (long idx=N; idx>0; idx--) {
// if no trains
if (ds[idx] == 0) {
ress[idx] = 1;
continue;
}
xp = min(xs[idx], (N-idx)/ds[idx]);
if (xp == 0) {
ress[idx] = 1;
continue;
}
res = 1;
// now loop
for (long p=1; p<=xp; p++) {
res += ress[idx+ds[idx]*p];
}
// add to memo
ress[idx] = res;
}
/*cout << "DEBUG: ";
for (int i=1; i<=N; i++) {
cout << ress[i] << ' ';
}
cout << endl;*/
cout << ress[1] << '\n';
return 0;
}
