#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef vector<int> vi;
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define all(x) x.begin(), x.end()
#define sz(x) (ll)(x).size()
constexpr ll inf = 4e18;
mt19937 mt(time(0));
const ll mod = 1000000007;
const ll SQRT = 300;
void solve() {
ll n; cin >> n;
vector<pll> trains(n);
for (ll i = 0; i < n; i++) {
auto &[d, k] = trains[i];
cin >> d >> k;
if (d > 0 && k > 0) {
ll mxk = (n - i - 1) / d;
k = min(k, mxk);
}
assert(i + k * d < n);
}
vector<ll> dp(n, 1);
vector<vector<ll>> sdp(SQRT, vector<ll>(n + SQRT));
for (ll i = n; i--;) {
auto &[d, k] = trains[i];
if (d < SQRT) {
dp[i] = ((sdp[d][i + d] - sdp[d][i + d + k * d] + 1) % mod + mod) % mod;
}
else {
for (ll j = 1; j <= k; j++) {
(dp[i] += dp[i + j * d]) %= mod;
}
}
for (ll j = 1; j < SQRT; j++) {
sdp[j][i] = (sdp[j][i + j] + dp[i]) % mod;
}
}
cout << dp[0] << '\n';
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
solve();
}
