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#include <bits/stdc++.h>
#define FOR(i, a, b) for(int i =(a); i < (b); ++i)
#define re(i, n) FOR(i, 1, n)
#define ford(i, a, b) for(int i = (a); i >= (b); --i)
#define rep(i, n) for(int i = 0;i <(n); ++i)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef vector<ll> vll;
typedef vector<int> vi;
typedef vector<pll> vpll;
typedef vector<pii> vpii;

const ll inf = 1e18;
const int N = 90'000;
const int mod = 1e9 + 7;

template<int N>
struct bit_array
{
    const static int arsz = (N >> 6) + 1;
    unsigned long long arr[arsz] = {0};
    void set(int pos)
    {
        arr[pos >> 6] |= (1ull << (pos & 0x0000003F));
    }
    void operator|=(const bit_array<N>& b)
    {
        rep(i, arsz) arr[i] |= b.arr[i];
    }
    int count()
    {
        int ret = 0;
        rep(i, arsz) ret += __builtin_popcount(arr[i]);
        return ret;
    }
};

struct event
{
    int height;
    int type;
};

set<int> sweep;
vector<event> events;
vector<vi> Adj;
bitset<N> dp[N];
ll fact[N];
ll factinv[N];
int dp2[N];

inline ll c(ll n, ll k)
{
    return (((fact[n] * factinv[n-k]) % mod) * factinv[k]) % mod;
}


ll pmod(ll x, ll exp)
{
    x %= mod;
    ll ret = 1ll;
    while (exp)
    {
        if (exp & 1)
        {
            ret *= x;
            ret %= mod;
        }
        exp >>= 1;
        x *= x;
        x %= mod;
    }
    return ret;
}

ll minv(ll x)
{
    return pmod(x, mod - 2);
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n;
    cin >> n;
    events.resize(2*n);
    Adj.resize(n);
    fact[0] = 1ll;
    rep(i, n)
    {
        fact[i+1] = fact[i] * (i+1);
        fact[i+1]  %= mod;
    }
    rep(i, n + 1)
    {
        factinv[i] = minv(fact[i]);
    }
    rep(i, 2*n)
    {
        events[i].type = -1;
    }
    rep(i, n)
    {
        int l, r;
        cin >> l >> r;
        l--;
        r--;
        event start;
        start.height = i;
        start.type = 0;
        event end;
        end.height = i;
        end.type = 1;
        events[l] = start;
        events[r] = end;
    }
    rep(i, 2*n)
    {
        if (events[i].type != -1)
        {
            int h = events[i].height;
            auto it = sweep.upper_bound(-h);
            if (it != sweep.end())
                Adj[h].push_back({-(*it)});
            if (events[i].type == 0)
            {
                sweep.insert(-h);
            }
            else
            {
                sweep.erase(-h);
            }
        }
    }
    /*rep(i, n)
    {
        cout << (i + 1) << ": ";
        for (int u : Adj[i])
        {
            cout << (u + 1) << " ";
        }
        cout << '\n';
    }*/
    for (int i = n - 1; i >= 0; i--)
    {
        int v = i;
        dp2[v] = dp[v].count();
        dp[v].set(v);
        for (int u : Adj[v]) dp[u] |= dp[v];
    }
    ll ans = 0ll;
    rep(i, n)
    {
        ll loc = c(n, dp2[i] + 1);
        loc *= fact[dp2[i]];
        loc %= mod;
        loc *= fact[n-dp2[i] - 1];
        loc %= mod;
        ans += loc;
        ans %= mod;
    }
    cout << ((ans * factinv[n]) % mod) << '\n';
}