#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define orta (bas + son >> 1)
#define sag (k + k + 1)
#define sol (k + k)
#define endl '\n'
#define foreach(i,x) for(type(x)i=x.begin();i!=x.end();i++)
#define FOR(ii,aa,bb) for(int ii=aa;ii<=bb;ii++)
#define ROF(ii,aa,bb) for(int ii=aa;ii>=bb;ii--)
#define mp make_pair
#define nd second
#define st first
#define type(x) __typeof(x.begin())
typedef pair < int ,int > pii;
typedef long long ll;
const long long linf = 1e18+5;
const int mod = (int) 1e9 + 7;
const int logN = 17;
const int inf = 1e9 + 7;
const int N = 2e5 + 5;
int F[N], P[N], con[N], m, pre[N], n, l, r, x, y, z, dp[N], dd[505][505];
map< int , vector< int > > add, del;
map< int , int > H;
vector< int > v;
int FE(int x, int k) {
if(!k) return 1;
int temp = FE(x, k / 2);
if(k & 1) return (ll) temp * temp % mod * x % mod;
return (ll) temp * temp % mod;
}
int GO(int x, int y) {
int ans = 1;
FOR(i, 1, y) ans = ans * (ll) x-- % mod;
return ans;
}
void calc(int x) {
FOR(i, 1, m) {
con[i] = GO(x, i) * (ll) F[i] % mod;
}
}
int NX(type(H) it) {
it++;
if(it == H.end()) return inf + 5;
return it->st;
}
int f(int x, int y) {
if(y == 0 || x == 0 || y > x) return 0;
int &r = dd[x][y];
if(r != -1) return r;
if(y == 1) return r = (pre[v[x] - 1] + f(x - 1, y)) % mod;
return r = (f(x - 1, y) + f(x - 1, y - 1)) % mod;
}
int main() {
//~ freopen("file.in","r",stdin);
scanf("%d", &n);
P[0] = 1;
FOR(i, 1, n) P[i] = P[i-1] * (ll) i % mod;
FOR(i, 0, n) F[i] = FE(P[i], mod - 2);
FOR(i, 1, n) {
scanf("%d %d", &l, &r);
add[l].pb(i);
del[r + 1].pb(i);
H[l] = H[r + 1] = 1;
}
set< int > S;
foreach(tt, H) {
int p = tt->st, next = NX(tt);
foreach(it, add[p]) S.insert(*it);
foreach(it, del[p]) S.erase(S.find(*it));
if(S.size()) {
v.clear();
pre[0] = 1; FOR(i, 1, n) pre[i] = (dp[i] + pre[i-1]) % mod;
v.pb(0); foreach(it, S) v.pb(*it);
m = v.size() - 1;
calc(next - p);
memset(dd, -1, sizeof dd);
FOR(i, 1, m)
FOR(j, 1, i) {
if(j == 1) {
dp[v[i]] = (dp[v[i]] + con[j] * (ll) pre[v[i] - 1]) % mod;
}
else {
dp[v[i]] = (dp[v[i]] + con[j] * (ll) f(i - 1, j - 1)) % mod;
}
}
}
}
dp[0] = 0;
FOR(i, 1, n) dp[i] = (dp[i] + dp[i-1]) % mod;
cout << dp[n] << endl;
return 0;
}
