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#include <bits/stdc++.h>
using namespace std;
using ll = long long;

///////////////////////
ll P = 1e9 + 7;
ll fastexp(ll base, ll exp, ll mod) {
    if(exp == 0)
        return 1;
    if(exp % 2 == 0) {
        ll t = fastexp(base, exp / 2, mod);
        return (t * t) % mod;
    } else {
        return (base * fastexp(base, exp - 1, mod)) % mod;
    }
}

ll inverse_mod_prime(ll a, ll p) {
    return fastexp(a, p - 2, p);
}

ll factorials[500000];

void init() {
    factorials[0] = 1;
    for(ll i = 1; i < 500000; i++) {
        factorials[i] = (i * factorials[i - 1]) % P;
    }
}
///////////////////////

int n;
vector<int> l, r;
vector<vector<int>> E;


void dfs(int x, vector<bool>& visited, int& count) {
    if(visited[x])
        return;
    visited[x] = true;
    count++;
    for(int child : E[x]) {
        dfs(child, visited, count);
    }
}

int main() {
    init();
    cin >> n;
    l = vector<int>(n + 1);
    r = vector<int>(n + 1);
    E = vector<vector<int>>(n + 1);
    for(int i = 1; i <= n; i++) {
        cin >> l[i] >> r[i];
    }
    map<int, int> water_lines;
    for(int x = n; x >= 1; x--) {
        //for(auto p : water_lines) {
        //    std::cerr << std::format("({}, {}) ", p.first, p.second);
        //}
        //std::cerr << "\n";
        for(auto ptr = water_lines.lower_bound(l[x]); ptr != water_lines.upper_bound(r[x]); ptr++) {
            //E[ptr->second].push_back(x);
            E[x].push_back(ptr->second);
            //std::cerr << ptr->second << " -> " << x << "\n";
        }
        water_lines.erase(water_lines.lower_bound(l[x]), water_lines.upper_bound(r[x]));
        water_lines[l[x]] = x;
        water_lines[r[x]] = x;
    }
    vector<int> upward_counts(n + 1, -1);
    for(int x = 1; x <= n; x++) {
        vector<bool> visited(n + 1, false);
        dfs(x, visited, upward_counts[x]);
        //std::cerr << x << " " << upward_counts[x] << "\n";
    }

    ll total = 0;
    for(int x = 1; x <= n; x++) {
        ll ci = n - 1 - upward_counts[x];
        assert(ci >= 0);
        assert(n - 1 >= ci);
        ll term = 0;
        for(int j = 0; j <= ci; j++) {
            term += (factorials[n - j - 1] * inverse_mod_prime(factorials[ci - j], P));
            term %= P;
        }
        term *= factorials[ci];
        term %= P;
        //std::cerr << x << " " << ci << " " << term << "\n";
        total += term * inverse_mod_prime(factorials[n], P) % P;
    }
    std::cout << total % P << "\n";
}