/***Farhan132***/
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
//#pragma GCC optimization ("unroll-loops")
//#pragma GCC optimize("Ofast,fast-math")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double dd;
typedef vector<ll> vll;
typedef pair<ll , ll> ii;
typedef vector< ii > vii;
typedef pair < pair < ll , ll > , pair < ll , ll > > cm;
typedef tuple < ll, ll, ll > tp;
#define ff first
#define ss second
#define pb push_back
#define in insert
#define f0(b) for(int i=0;i<(b);i++)
#define f00(b) for(int j=0;j<(b);j++)
#define f1(b) for(int i=1;i<=(b);i++)
#define f11(b) for(int j=1;j<=(b);j++)
#define f2(a,b) for(int i=(a);i<=(b);i++)
#define f22(a,b) for(int j=(a);j<=(b);j++)
#define sf(a) scanf("%lld",&a)
#define sff(a,b) scanf("%lld %lld", &a , &b)
#define pf(a) printf("%lld\n",a)
#define pff(a,b) printf("%lld %lld\n", a , b)
#define bug printf("**!\n")
#define mem(a , b) memset(a, b ,sizeof(a))
#define front_zero(n) __builtin_clzll(n)
#define back_zero(n) __builtin_ctzll(n)
#define total_one(n) __builtin_popcount(n)
#define clean fflush(stdout)
//const ll mod = (ll) 998244353;
const ll mod = (ll) 1e9 + 7;
const ll maxn = (ll)1e8 + 5;
const int nnn = 1048590;
const int inf = numeric_limits<int>::max()-1;
//const ll INF = numeric_limits<ll>::max()-1;
const ll INF = (ll)1e18;
ll dx[]={0,1,0,-1};
ll dy[]={1,0,-1,0};
ll dxx[]={0,1,0,-1,1,1,-1,-1};
ll dyy[]={1,0,-1,0,1,-1,1,-1};
bool USACO = 0;
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template <typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const ll N = 505;
ll fac[N], inv[N], num[N];
ll pw(ll a , ll b){
ll res = 1;
while(b){
if(b&1) res = (res*a)%mod;
a = (a*a)%mod;
b /= 2;
}
return res;
}
void pre(ll n){
fac[0] = 1;
inv[0] = pw(fac[0], mod - 2);
for(ll i = 1; i < n; i++){
fac[i] = (fac[i-1] * i)%mod;
inv[i] = pw(fac[i], mod - 2);
num[i] = pw(i, mod - 2);
}
return;
}
ll nCr(ll n , ll r){
if(n == r) return 1;
if(n < r) return 0;
ll ans = fac[n] * (inv[r]);
ans %= mod;
ans *= inv[n - r];
return ans%mod;
}
ll dp[N][2*N];
ll combo[2*N][N];
ll a[N] , b[N];
void solve(){
ll n; cin >> n;
vector < ll > idx; idx.pb(0); idx.pb(1);
for(ll i = 1; i <= n; i++){
cin >> a[i] >> b[i];
idx.pb(a[i]); idx.pb(b[i] + 1);
}
sort(idx.begin(), idx.end());
idx.erase(unique(idx.begin(), idx.end()), idx.end());
mem(dp, 0);
ll sz = idx.size();
for(ll i = 0; i < sz - 1; i++){
ll len = idx[i + 1] - idx[i];
for(ll j = 0; j <= n; j++){
combo[i][j] = 0;
ll res = 1, l = len;
for(ll x = 1; x <= j; x++){
res = (res * l)%mod; l--;
res = (res * num[x])%mod;
combo[i][j] += nCr(j - 1, x - 1) * res;
combo[i][j] %= mod;
}
}
}
for(ll i = 0; i < sz; i++) dp[0][i] = 1;
ll ans = 0;
for(ll i = 1; i <= n; i++){
a[i] = lower_bound(idx.begin(), idx.end(), a[i]) - idx.begin();
b[i] = upper_bound(idx.begin(), idx.end(), b[i]) - idx.begin() - 1;
dp[i][0] = 0;
for(ll x = a[i]; x <= b[i]; x++){
ll cnt = 1;
ll len = idx[x + 1] - idx[x];
for(ll j = i - 1; j >= 0; j--){
dp[i][x] += combo[x][cnt] * dp[j][x - 1];
dp[i][x] %= mod;
if(a[j] <= x && b[j] >= x) cnt++;
}
}
for(ll x = 1; x < sz; x++) dp[i][x] = (dp[i][x - 1] + dp[i][x])%mod;
ans += dp[i][sz-1];
}
cout << ans%mod << '\n';
return;
}
int main() {
#ifdef LOCAL
freopen("in", "r", stdin);
freopen("out", "w", stdout);
auto start_time = clock();
#else
ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
#endif
pre(N);
ll T = 1, CT = 0; //cin >> T;
while(T--){
// cout << "Case #" << ++CT <<": " ;
solve();
}
#ifdef LOCAL
auto end_time = clock();
cerr<< "Execution time: "<<(end_time - start_time)*(int)1e3/CLOCKS_PER_SEC<<" ms\n";
#endif
return 0;
}
