#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cmath>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include <cstdarg>
#include <cstdio>
#include <cstdlib>
using namespace std;
using ll = long long;
ll mod = 1e9 + 7;
ll gcd(ll a, ll b) {
if (b == 0)return a;
else return gcd(b, a % b);
}
void solve() {
ll n; cin >> n;
vector<ll>d(n), x(n);
for (ll i = 0; i < n; i++) {
cin >> d[i] >> x[i];
}
ll armat = 400;
vector<ll>dp(n);
dp[0] = 1;
vector<vector<ll>>pref(armat, vector<ll>(n));
for (ll i = 0; i < n; i++) {
for (ll j = 1; j < armat; j++) {
if (i - j >= 0) {
pref[j][i] += pref[j][i-j];
if (pref[j][i] >= mod)pref[j][i] -= mod;
}
dp[i] += pref[j][i];
if (dp[i] >= mod)dp[i] -= mod;
}
if (d[i] == 0)continue;
if (d[i] >= armat) {
for (ll j = i + d[i]; j <= min(n - 1, i + d[i] * x[i]); j += d[i]) {
dp[j] += dp[i];
if (dp[j] >= mod)dp[j] -= mod;
}
}
else {
if (i + d[i] < n) {
pref[d[i]][i + d[i]] += dp[i];
if (pref[d[i]][i + d[i]] >= mod)pref[d[i]][i + d[i]] -= mod;
}
if (i + d[i] * (x[i]+1) < n) {
pref[d[i]][i + d[i] * (x[i] + 1)] -= dp[i];
if (pref[d[i]][i + d[i] * (x[i] + 1)] < 0) pref[d[i]][i + d[i] * (x[i] + 1)] += mod;
}
}
}
ll ans = 0;
for (ll i = 0; i < n; i++) {
ans += dp[i];
if (ans >= mod)ans -= mod;
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(nullptr);
cout.tie(nullptr);
ll t = 1;
//cin >> t;
while (t--) {
solve();
}
}
