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#pragma GCC optimize("unroll-loops")
#pragma GCC target("popcnt,avx,tune=native")
#include <bits/stdc++.h>
using namespace std;
 
#define fwd(i, a, n) for (int i = (a); i < (n); i ++)
#define rep(i, n) fwd(i, 0, n)
#define all(X) begin(X), end(X)
#define sz(X) ((int)X.size())
#define st first
#define nd second
#define pii pair<int, int>
#define vi vector<int>
#define ll long long
 
#ifdef LOC
auto &operator<<(auto &out, pair<auto, auto> a) {
	return out << "(" << a.st << ", " << a.nd << ")";
}
 
auto &operator<<(auto &out, auto a) {
	out << "{";
	for (auto b : a)
		out << b << ", ";
	return out << "}";
}
 
void dump(auto... x) { ((cerr << x << ", "), ...) << '\n'; }
#define debug(x...) cerr << __LINE__ << ": [" #x "]: ", dump(x)
#else
#define debug(...) 0
#endif

struct Tree{
    private:
    int lrSize = 2;
    vector<int> v;
    vector<int> time;
    int t = 1;

    void setRange(int a, int b, int l, int r, int pos, int val){
        if(r < a || b < l)return;
        if(a <= l && r <= b){
            v[pos] = val;
            time[pos] = t++;
            return;
        }
        int m = (l + r)/2;
        setRange(a, b, l, m, 2*pos, val);
        setRange(a, b, m+1, r, 2*pos + 1, val);
    }

    public:
    Tree(int n){
        while(lrSize < n)lrSize *= 2;
        //debug(lrSize);
        v.resize(2*lrSize, -1);
        time.resize(2*lrSize, 0);
    }

    void print(){
        for(int h = 1; h <= lrSize; h*=2){
            for(int i = h; i < 2*h; i++)cout<<v[i]<<" ";
            cout<<"\n";
        }
    }

    void set(int a, int b, int val){
        setRange(a, b, 1, lrSize, 1, val);
        //print();
        //debug(v);
    }

    int query(int pos){
        pos += lrSize - 1;
        int ans = v[pos];
        int tim = time[pos];
        //debug(pos);
        while(pos > 1){
            pos /= 2;
            //debug(pos);
            if(time[pos] > tim){
                ans = v[pos];
                tim = time[pos];
            }
        }
        return ans;
    }
};

const int K = 512;

const ll MOD = 1e9 + 7;

long long power(long long a, long long b){
    long long res = 1;
    while(b){
        while(!(b&1)){
            a = (a * a) % MOD;
            b>>=1;
        }
        res = (res * a) % MOD;
        b--;
    }
    return res;
}
 
int32_t main() {
	ios_base::sync_with_stdio(0), cin.tie(0);
    int n; cin>>n;
    vector<int> l(n);
    vector<int> r(n);
    Tree tree(2*n);
    vector<ll> inv(n+1);
    vector<ll> fact(n+1);
    fact[0] = 1;
    for(ll i = 1; i <= n; i++)fact[i] = (fact[i-1] * i) % MOD;
    ll x = power(fact[n], MOD - 2);
    for(ll i = n; i >= 1; i--){
        inv[i] = (x * fact[i-1]) % MOD;
        x = (x * i) % MOD;
    }
    rep(i, n){
        int a, b; cin>>a>>b;
        //debug(a, b);
        l[n-1-i] = tree.query(a);
        r[n-1-i] = tree.query(b);
        //debug(l[n-1-i], r[n-1-i]);
        tree.set(a, b, n-1-i);
    }
    //debug(l);
    //debug(r);
    vector<int> cnt(n, 0);
    vector<bitset<K>> v(n);
    for(int i =0; i < n; i+= K){
        for(int j= i; j < i + K && j < n; j++){
            v[j][j-i] = 1;
        }
        for(int j = i; j < n; j++){
            if(l[j] != -1){
                v[l[j]] |= v[j];
            }
            if(r[j] != -1 && r[j] != l[j]){
                v[r[j]] |= v[j];
            }
            cnt[j] += v[j].count();
        }
        for(int j= i; j < n; j++){
            v[j].reset();
        }
    }
    //debug(cnt);
    long long ans = 0;
    rep(i, n)ans = (ans + inv[cnt[i]]) % MOD;
    cout<<ans<<"\n";
	return 0;
}