#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define bitcount __builtin_popcountll
#define all(a) (a).begin(), (a).end()
using namespace std;
using namespace __gnu_pbds;
template<typename T> using ordered_multiset = tree<T, null_type, less_equal<T>, rb_tree_tag, tree_order_statistics_node_update>;
const int MOD = 1e9+7;
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr); cout.tie(nullptr);
int n; cin>>n;
int jump[n], lim[n];
for (int i = 0; i < n; cin>> jump[i] >> lim[i++]);
int dp[n]{};
for (int i = n-1; i >= 0; i--) {
dp[i] = 1;
if (jump[i] == 0) continue;
for (int j = 1; j <= lim[i] && i + j*jump[i] < n; j++) {
dp[i] += dp[i + j*jump[i]];
if (dp[i] >= MOD) dp[i] -= MOD;
}
}
cout<<dp[0];
}
