#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<queue>
#include<map>
using namespace std;
using ll = long long;
ll gcd(ll a, ll b)
{
return b ? gcd(b, a % b) : a;
}
ll mod = 1e9 + 7;
void solve() {
ll n; cin >> n;
vector<vector<ll>>gp(n);
vector<ll>d(n),x(n);
int f = 0;
for (ll i = 0; i < n; i++) {
cin >> d[i] >> x[i];
if (d[i] != 1)f = 1;
if (d[i] == 0)continue;
for (ll j = 1; j <= x[i]; j++) {
if (i + j * d[i] < n) {
gp[i].push_back(i + j * d[i]);
}
else break;
}
}
if (f == 0) {
ll ans = 0, aper = 0;
vector<ll>pref(n + 10);
pref[0] = 1;
pref[1] = -1;
for (ll i = 0; i < n; i++) {
pref[i] %= mod;
aper += pref[i];
aper %= mod;
pref[i + 1] += aper;
pref[min(n, i + x[i] + 1)] -= aper;
ans += aper;
ans %= mod;
}
cout << ans << endl;
}
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
//signed _; cin >> _; while (_--)
solve();
}
