#include <bits/stdc++.h>
using namespace std;
using ll=long long;
#define F first
#define S second
#define sz(x) int(x.size())
const ll MOD=1e9+7;
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n;
cin >> n;
vector<ll> d(n+1), x(n+1);
for(int i=1; i<=n; i++) {
cin >> d[i] >> x[i];
}
vector<ll> o(n+1);
o[1]=1;
ll s=1;
for(int i=2; i<=n; i++) {
for(int j=1; j<i; j++) {
if(d[j]!=0 && i%d[j]==j%d[j] && (i-j)/d[j]<=x[j]) {
o[i]=(o[i]+o[j])%MOD;
}
}
s=(s+o[i])%MOD;
}
cout << s << '\n';
return 0;
}
