#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int mod = 1e9+7, N = 1e5;
ll dp[N];
int main() {
int n;
cin >> n;
vector<int> d(n), x(n);
for (int i = 0; i < n; ++i) cin >> d[i] >> x[i];
dp[0] = 1;
for (int i = 1; i < n; ++i) {
for (int j = 0; j < i; ++j) {
if (!d[j]) continue;
if ((i-j)%d[j] == 0 && (i-j)/d[j] <= x[j]) dp[i]+=dp[j];
dp[i] %= mod;
}
}
ll tot = 0;
for (int i = 0; i < n; ++i) tot += dp[i];
cout << tot << endl;
return 0;
}
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