/*
Code written by Talant I.D.
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
#define precision(n) fixed << setprecision(n)
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define mp make_pair
#define eps (double)1e-9
#define PI 2*acos(0.0)
#define endl "\n"
#define sz(v) int((v).size())
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define OK cout << "OK" << endl;
const int mod = 1e9+7;
ll mode(ll a) {
a %= mod;
if (a < 0) a += mod;
return a;
}
ll subt(ll a, ll b) {
return mode(mode(a)-mode(b));
}
ll add(ll a, ll b) {
return mode(mode(a)+mode(b));
}
ll mult(ll a, ll b) {
return mode(mode(a)*mode(b));
}
ll binpow(ll a, ll b) {
ll res = 1;
while (b) {
if (b&1) res = mult(res, a);
a = mult(a, a);
b >>= 1;
}
return res;
}
const int N = 503;
int a[N], b[N], n;
bool subtask1() {
int flag = 0;
for (int i = 1; i <= n; i++) {
if (a[i] == b[i]) flag++;
}
return flag == n;
}
bool subtask2() {
ll sum = 0;
for (int i = 1; i <= n; i++) {
sum += b[i]-a[i];
}
return sum <= 1e6;
}
struct node {
ll val;
int lson, rson;
node() {
val = 0;
lson = rson = -1;
}
} tree[8000007];
int vertices = 1;
void create_lson(int v) {
if (tree[v].lson == -1) {
tree[v].lson = ++vertices;
}
}
void create_rson(int v) {
if (tree[v].rson == -1) {
tree[v].rson = ++vertices;
}
}
void update(int v, int l, int r, int pos, ll val) {
if (l == r) {
tree[v].val = add(tree[v].val, val);
return;
}
int mid = (l+r) >> 1;
create_lson(v);
create_rson(v);
if (pos <= mid) update(tree[v].lson, l, mid, pos, val);
else update(tree[v].rson, mid+1, r, pos, val);
tree[v].val = add(tree[tree[v].lson].val, tree[tree[v].rson].val);
}
ll get(int v, int l, int r, int ql, int qr) {
if (l > qr || ql > r) return 0;
if (ql <= l && r <= qr) return tree[v].val;
int mid = (l+r) >> 1;
create_lson(v);
create_rson(v);
return add(get(tree[v].lson, l, mid, ql, qr), get(tree[v].rson, mid+1, r, ql, qr));
}
int main() {
do_not_disturb
cin >> n;
for (int i = 1; i <= n; i++) {
cin >> a[i] >> b[i];
}
if (subtask1()) {
vector <ll> dp(n+1);
dp[0] = 1;
for (int i = 1; i <= n; i++) {
for (int j = i-1; j >= 0; j--) {
if (a[i] > a[j]) {
dp[i] = add(dp[i], dp[j]);
}
}
}
ll ans = 0;
for (int i = 1; i <= n; i++) {
ans = add(ans, dp[i]);
}
cout << ans << endl;
return 0;
}
else if (subtask2()) {
vector <vector <ll>> dp(n+1);
dp[0].pb(1);
update(1, 0, 1e9, 0, 1);
ll ans = 0;
for (int i = 1; i <= n; i++) {
for (int j = a[i]; j <= b[i]; j++) {
dp[i].pb(get(1, 0, 1e9, 0, j-1));
}
for (int j = a[i]; j <= b[i]; j++) {
update(1, 0, 1e9, j, dp[i][j-a[i]]);
}
}
for (int i = 1; i <= n; i++) {
for (auto to : dp[i]) ans = add(ans, to);
}
cout << ans << endl;
return 0;
}
return 0;
}
