#include <bits/stdc++.h>
#define int long long
int mod = 1e9 + 7;
int add(int x, int y) {
x += y;
if(x < 0) {
x += mod;
}
if(x >= mod) {
x %= mod;
}
return x;
}
int S = 280;
const int N = 1e5 + 5;
signed main() {
int n;
std::cin >> n;
std::vector<int> d(n + 1), x(n + 1);
for(int i = 1; i <= n; i++) {
std::cin >> d[i] >> x[i];
}
std::vector<int> dp(n + 1, 0);
dp[1] = 1;
std::vector<std::vector<int>> pref(n + 2, std::vector<int>(S));
for(int i = 1; i <= n; i++) {
if(d[i] == 0) {
continue;
}
int e = std::min(x[i], (n - i + 1) / d[i]);
for(int t = 1; t < S; t++) {
if(i - t >= 0) {
pref[i][t] = add(pref[i][t], pref[i - t][t]);
dp[i] = add(dp[i], pref[i][t]);
}
}
if(d[i] >= S) {
for(int t = 1; t <= x[i] && i + t * d[i] <= n; t++) {
dp[i + t * d[i]] = add(dp[i + t * d[i]], dp[i]);
}
}
else {
if(e <= S) {
for(int t = 1; t <= x[i] && i + t * d[i] <= n; t++) {
dp[i + t * d[i]] = add(dp[i + t * d[i]], dp[i]);
}
}
else {
int w = std::min(n, i + x[i] * d[i]);
pref[i][d[i]] = add(pref[i][d[i]], dp[i]);
if(w + d[i] <= n) {
pref[w + d[i]][d[i]] = add(pref[w + d[i]][d[i]], - dp[i]);
}
}
}
}
int ans = 0;
for(int i = 1; i <= n; i++) {
ans = add(ans, dp[i]);
}
std::cout << ans;
}
