#include <bits/stdc++.h>
#define int long long
using namespace std;
const int MOD = 1e9 + 7;
struct Ville {
int raison, nbStops;
};
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int nbVilles;
cin >> nbVilles;
vector<Ville> villes(nbVilles);
for(Ville& ville : villes) {
cin >> ville.raison >> ville.nbStops;
}
reverse(villes.begin(), villes.end());
vector<int> reponses;
for(int iVille = 0;iVille < nbVilles;iVille++) {
int nbChemins = 1;
Ville& v = villes[iVille];
if(v.raison != 0) {
for(int stop = 1;stop <= v.nbStops;stop++) {
int pos = iVille - stop * v.raison;
if(pos < 0) break;
nbChemins += reponses[pos];
}
nbChemins %= MOD;
}
reponses.push_back(nbChemins);
}
cout << reponses.back() << endl;
return 0;
}
