# include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
#define int long long
#define pii pair <int, int>
#define pb push_back
const int N = 1005, mod = 1e9 + 7;
int t,n,a[N],b[N],pr[N][N],dp[N][N],inv[N],fq[N],ch[N][N],chh[N][N],sum[N][N];
map <int, int> shes;
vector <int> v;
int f_p(int base, int power) {
int result = 1;
while (power > 0) {
if (power % 2) result = (result * base) % mod;
base = (base * base) % mod;
power /= 2;
}
return result;
}
int C(int n, int k) {
if (n < k) return 0;
if (n == 0 && k == 0) return 1;
int pas = 1;
for (int i = n; i >= n - k + 1; i--){
pas *= i;
pas %= mod;
}
pas *= inv[k];pas %= mod;
return pas;
}
int check(int le, int ri, int a, int b) {
return (max(a,le) <= min(b,ri));
}
main() {
std::ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0);
cin>>n;
for (int i = 1; i <= n; i++) {
cin>>a[i]>>b[i];
v.pb(a[i]);
v.pb(b[i] + 1);
}
fq[0] = 1; inv[0] = 1;
for (int i = 1; i < N; i++) {
fq[i] = fq[i - 1] * i % mod;
}
inv[N - 1] = f_p(fq[N - 1], mod - 2);
for (int i = N - 2; i >= 1; i--) {
inv[i] = (inv[i + 1] * (i + 1)) % mod;
}
sort(v.begin(), v.end());
v.resize(unique(v.begin(), v.end())-v.begin());
vector <pii> seg;
vector <int> szz;
seg.pb({-1,-1});
for (int i = 1; i < v.size(); i++) {
seg.pb({v[i - 1], v[i] - 1});
szz.pb(v[i] - v[i - 1]);
}
sort(szz.begin(), szz.end());
szz.resize(unique(szz.begin(), szz.end())-szz.begin());
dp[0][0] = 1;
pr[0][0] = 1;
ch[0][0] = 1;
ch[1][1] = ch[1][0] = 1;
for (int i = 2; i <= n; i++) {
ch[i][0] = 1;
for (int j = 1; j <= i; j++) {
ch[i][j] = (ch[i - 1][j] + ch[i - 1][j - 1]) % mod;
}
}
int raod = 0;
for (int sz : szz) { raod++; shes[sz] = raod;
for (int cnt = 1; cnt <= n; cnt++) {
chh[raod][cnt] = C(sz, cnt);
for (int cn = 1; cn <= cnt; cn++) {
sum[raod][cnt] += chh[raod][cn] * ch[cnt - 1][cn - 1] % mod;
if (sum[raod][cnt] >= mod) sum[raod][cnt] -= mod;
}
}
}
int ans = 0;
for (int i = 1; i < seg.size(); i++) pr[0][i] = 1;
for (int i = 1; i <= n; i++) {
for (int j = 1; j < seg.size(); j++) {
int le = seg[j].f; int ri = seg[j].s;
if (check(le,ri,a[i],b[i])) {
int cnt = 1;
int sh = shes[ri - le + 1];
for (int prless = i - 1; prless >= 0; prless--) {
dp[i][j] += sum[sh][cnt] * pr[prless][j - 1] % mod;
//cout<<i<<" "<<j<<" "<<ri - le + 1<<" "<<cnt<<" "<<sum[ri - le + 1][cnt]<<" "<<pr[prless][j - 1]<<endl;
if (dp[i][j] >= mod) dp[i][j] -= mod;
if ((check(le,ri,a[prless],b[prless]))) cnt++;
}
}
ans += dp[i][j]; if (ans >= mod) ans -= mod;
pr[i][j] = (dp[i][j] + pr[i][j - 1]); if (pr[i][j] >= mod) pr[i][j] -= mod;
}
}
cout<<ans<<"\n";
}
