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

#define int long long
#define ll long long
#define ld long double
#define pb push_back
#define nd second
#define st first
#define sz size
#define forr(i, n) for(int i=1;i<=n;i++)
const ll infl=1e18+90;
const int inf=1e9+90;
const int roz=2e5+93;
const int mod=1e9+7;

int sil[roz], odwrot[roz];


long long binpow(long long a, long long b, long long mod) {
    a %= mod;
    long long res = 1;
    while (b > 0) {
        if (b & 1)
            res = res * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return res;
}

void silnie()
{
    sil[0]=1;
    odwrot[0]=1;
    for(int i=1;i<=roz-60;i++)
    {
        sil[i]=sil[i-1]*i;
        sil[i]%=mod;
        odwrot[i]=binpow(sil[i], mod-2, mod);
    }
}

int fun(int a, int b)
{
    return ((sil[a]*odwrot[b])%mod*odwrot[a-b])%mod;
}

set<pair<int,int> > S;
set<int> graf[roz];
vector<pair<int,int> > wek, do_wyj;
int ile[roz], odw[roz];

void dfs(int u, int x)
{
    //cerr<<"wchodze dla u = "<<u<<" x = "<<x<<"\n";
    ile[u]++;
    odw[u]=x;
    for(auto v:graf[u])
    {
        if(odw[v]!=x) dfs(v, x);
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    int n;
    cin>>n;
    silnie();
    for(int i=1;i<=n;i++)
    {
        int a, b;
        cin>>a>>b;
        wek.pb({a, b});
    }
    reverse(wek.begin(), wek.end());
    for(int i=1;i<=n;i++)
    {
        int a=wek[i-1].st, b=wek[i-1].nd;
        for(auto [c, d]:S)
        {
            if(c>a&&c<b)
            {
                graf[d].insert(i);
                do_wyj.pb({c, d});
            }
        }
        for(auto x:do_wyj)
        {
            S.erase(x);
        }
        do_wyj.clear();
        S.insert({a, i});
        S.insert({b, i});
    }
    for(int i=1;i<=n;i++)
    {
        dfs(i, i);
    }
    int wyn=0;
    for(int i=1;i<=n;i++)
    {
        int y=ile[i]-1;
        for(int j=1;j<=n-y;j++)
        {
            wyn+=((sil[n-1-y]*sil[n-j])%mod*odwrot[n-y-j])%mod;
            wyn%=mod;
        }
    }
    wyn*=odwrot[n];
    wyn%=mod;
    cout<<wyn<<"\n";
}