#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
const int mod = 1e9 + 7;
#define fr first
#define sc second
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
int b = sqrt(n);
vector<pair<int, int>> train(n);
for(int i = 0; i < n; i ++)
{
cin >> train[i].fr >> train[i].sc;
train[i].fr = min(n + 5, train[i].fr);
train[i].sc = min(n + 5, train[i].sc);
}
vector<int> dp(n + 3, 1);
vector<vector<int>> dp2(n + 3, vector<int>(b + 3, 0));
for(int i = n - 1; i >= 0; i --)
{
if(train[i].fr == 0 || train[i].sc == 0)
{
for(int j = 1; j <= b; j ++)
{
if(i + j < n)
dp2[i][j] = dp2[i + j][j];
dp2[i][j] += dp[i];
dp2[i][j] %= mod;
}
continue;
}
if(train[i].fr >= b)
{
for(int j = 1; j <= train[i].sc && train[i].fr * j + i < n; j ++)
{
dp[i] += dp[j * train[i].fr + i];
dp[i] %= mod;
}
}
else
{
if(i + train[i].fr < n)
dp[i] += dp2[i + train[i].fr][train[i].fr];
if(i + train[i].fr * (train[i].sc + 1) < n)
dp[i] -= dp2[i + train[i].fr * (train[i].sc + 1)][train[i].fr];
dp[i] %= mod;
dp[i] += mod;
dp[i] %= mod;
}
for(int j = 1; j <= b; j ++)
{
if(i + j < n)
dp2[i][j] = dp2[i + j][j];
dp2[i][j] += dp[i];
dp2[i][j] %= mod;
}
}
cout << dp[0];
return 0;
}
