#include <iostream>
#include <vector>
#include <numeric>
#include <unordered_map>
#define ll long long
using namespace std;
ll mod = 1000000007;
int main() {
int n; cin >> n;
vector <ll> d(n + 1);
vector <ll> x(n + 1);
for (int i = 1; i <= n; i++) {
cin >> d[i] >> x[i];
}
vector <ll> dp(n + 1, 0);
dp[1] = 1;
vector <unordered_map<ll, ll>> m(n + 1);
for (int i = 1; i <= n; i++) {
for (auto j : m[i]) {
dp[i] += j.second;
dp[i] %= mod;
if (i + j.first <= n) {
if (m[i + j.first].count(j.first)) {
m[i + j.first][j.first] += j.second;
m[i + j.first][j.first] %= mod;
} else {
m[i + j.first][j.first] = j.second;
m[i + j.first][j.first] %= mod;
}
}
}
if (d[i] != 0) {
if (i + d[i] <= n) {
if (m[i + d[i]].count(d[i])) {
m[i + d[i]][d[i]] += dp[i];
m[i + d[i]][d[i]] %= mod;
} else {
m[i + d[i]][d[i]] = dp[i];
m[i + d[i]][d[i]] %= mod;
}
}
if (i + d[i] * (x[i] + 1) <= n) {
if (m[i + d[i] * (x[i] + 1)].count(d[i])) {
m[i + d[i] * (x[i] + 1)][d[i]] += -dp[i] + mod;
m[i + d[i] * (x[i] + 1)][d[i]] %= mod;
} else {
m[i + d[i] * (x[i] + 1)][d[i]] = -dp[i] + mod;
m[i + d[i] * (x[i] + 1)][d[i]] %= mod;
}
}
}
}
ll ans = 0;
for (int i = 1; i <= n; i++) {
ans += dp[i];
ans %= mod;
}
cout << ans;
return 0;
}
