#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> v2i;
typedef pair<int, int> pi;
typedef vector<ll> vl;
#define pb push_back
#define mp make_pair
#define rep(i, n) for (int i = 0; i < n; i++)
const ll p = 1e9 + 7;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n, di, xi;
vl d, x;
cin >> n;
rep(i, n) {
cin >> di >> xi;
d.pb(di); x.pb(xi);
}
vl dp = { 1 };
ll total = 1;
for (int i = 1; i < n; i++)
{
ll t = 0;
for (int j = 0; j < i; j++)
{
if (d[j] != 0) {
if ((i-j) % d[j] == 0 && i-j <= d[j] * x[j]) {
t += dp[j];
t %= p;
//cout << i << " can be reached by " << j << "\n";
}
}
}
dp.pb(t);
total += t;
total %= p;
//cout << "calculated " << i << " as " << t << "\n";
}
cout << total;
return 0;
}
