#include <bits/stdc++.h>
//#define DEBUG 1106
#define int long long
#define ll long long
#define ld long double
#define pb emplace_back
#define p_q priority_queue
#define m_p make_pair
#define pii pair<int,int>
#define endl '\n'
#define INIT ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define FOR(i,a,b) for(int i = a; i <= b; i++)
#define forn(i,n) for (int i = 0; i < n; i++)
#define forn1(i,n) for (int i = 1; i <= n; i++)
#define all(x) x.begin(),x.end()
#define ft first
#define sd second
#define lowbit(x) (x&(-x))
#define chmax(x,y) x=max(x,y)
#define chmin(x,y) x=min(x,y)
#ifdef DEBUG
#define debug(x) cout << #x << ": " << x << endl;
#else
#define debug(x) 1106;
#endif
using namespace std;
const int N = 2e5+5;
const int inf = 1e9;
const int INF = 1e18;
const int MOD = 1e9+7;
int d[N], x[N];
int a[N];
signed main() {
INIT
#ifdef DEBUG
freopen("input.txt", "r", stdin);
#endif
///////////
int n;
cin >> n;
forn(i,n) {
cin >> d[i] >> x[i];
}
a[0] = 1;
forn(i,n) {
if(d[i]==0) continue;
forn1(j,x[i]) {
if(i+j*d[i]>=n) break;
a[i+j*d[i]] += a[i];
a[i+j*d[i]] %= MOD;
}
}
int ans = 0;
forn(i,n) {
//cout << a[i] << ' ';
ans += a[i];
ans = ans%MOD;
}
//cout << '>';
cout << (ans+MOD+MOD)%MOD;
}
