#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define ALL(v) (v).begin(), (v).end()
#define MASK(i) (1LL << (i))
#define GETBIT(mask, i) (((mask) >> (i)) & 1)
// mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng(1);
ll rngesus(ll l, ll r){return ((ull) rng()) % (r - l + 1) + l;}
ll max(ll a, ll b){return (a > b) ? a : b;}
ll min(ll a, ll b){return (a < b) ? a : b;}
ll LASTBIT(ll mask){return mask & (-mask);}
ll pop_cnt(ll mask){return __builtin_popcountll(mask);}
ll ctz(ll mask){return __builtin_ctzll(mask);}
ll clz(ll mask){return __builtin_clzll(mask);}
ll logOf(ll mask){return 63 - clz(mask);}
template <class T1, class T2>
bool minimize(T1 &a, T2 b){
if (a > b){a = b; return true;}
return false;
}
template <class T1, class T2>
bool maximize(T1 &a, T2 b){
if (a < b){a = b; return true;}
return false;
}
template <class T>
void printArr(T& a, string separator = " ", string finish = "\n", ostream& out = cout){
for(auto i: a) out << i << separator;
out << finish;
}
template <class T>
void remove_dup(vector<T> &a){
sort(ALL(a));
a.resize(unique(ALL(a)) - a.begin());
}
const long MOD = 1e9 + 7;
ll fast_pow(ll a, ll b){
ll ans = 1;
while(b > 0){
if (b & 1) ans = ans * a % MOD;
a = a * a % MOD;
b /= 2;
}
return ans;
}
ll inverse(ll a){return fast_pow(a, MOD - 2);}
const long N = 505;
ll fact[N], ifact[N];
void prepare(){
fact[0] = 1;
for(long i = 1; i<N; ++i) fact[i] = fact[i-1] * i % MOD;
ifact[N-1]= inverse(fact[N-1]);
for(long i = N-1; i>=1; --i) ifact[i-1] = ifact[i] * i % MOD;
}
ll C(long n, long k){
if (k < 0 || k > n) return 0;
return fact[n] * ifact[k] % MOD * ifact[n - k] % MOD;
}
ll eulerCandy(long s, long k){
return C(s + k - 1, k - 1);
}
ll normie(ll a){
a %= MOD;
if (a < 0) a += MOD;
return a;
}
void add(int &a, int b){
a += b;
if (a >= MOD) a -= MOD;
}
void sub(int &a, int b){
a -= b;
if (a < 0) a += MOD;
}
int dp[N * 2][N], s[N * 2][N];
int main(void){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
prepare();
int n; cin >> n;
vector<pair<int, int>> a(n);
for(int i= 0; i<n; ++i) cin >> a[i].first >> a[i].second;
vector<int> b;
for(pair<int, int> i: a){
b.push_back(i.first - 1);
b.push_back(i.second);
}
remove_dup(b);
vector<pair<int, int>> range;
range.push_back({0, 0});
for(int i= 1; i<(int)b.size(); ++i) range.push_back({b[i-1] + 1, b[i]});
a.insert(a.begin(), {0, 0});
dp[0][0] = 1;
for(int i= 0; i <= n; ++i) s[0][i] = 1;
for(int i= 0; i<range.size(); ++i) s[i][0] = 1;
for(int layer = 1; layer < (int)range.size(); ++layer){
int len = range[layer].second - range[layer].first + 1;
vector<int> fuck(min(n, len) + 1, 1);
for(int i = 1; i<(int)fuck.size(); ++i)
fuck[i] = 1LL * fuck[i-1] * (len - i + 1) % MOD;
for(int i = 1; i<(int)fuck.size(); ++i)
fuck[i] = 1LL * fuck[i] * ifact[i] % MOD;
vector<int> love(n+1);
love[1] = len;
for(int i = 2; i<=n; ++i){
for(int t = 2; t <= min(fuck.size() - 1, i); ++t){
add(love[i], 1LL * fuck[t] * C(i - 2, t - 2) % MOD);
}
}
for(int i = 1; i<=n; ++i){
if (a[i].first > range[layer].first || range[layer].second > a[i].second) continue;
int sum = s[layer - 1][i - 1];
int cnt = 0;
for(int j = i; j<=n; ++j){
if (a[j].first > range[layer].first || range[layer].second > a[j].second) continue;
cnt++;
dp[layer][j] = 1LL * sum * love[cnt] % MOD;
}
}
for(int i = 1; i<=n; ++i){
s[layer][i] = dp[layer][i];
add(s[layer][i], s[layer-1][i]);
add(s[layer][i], s[layer][i-1]);
sub(s[layer][i], s[layer-1][i-1]);
}
}
int ans = s[range.size() - 1][n];
sub(ans, 1);
cout << ans << "\n";
return 0;
}
