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#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <numeric>
#include <random>
/* #include "../../simple-console-debug/debug.h" */
using namespace std;
random_device rd;
int r(int a, int b) {
    return uniform_int_distribution<int>(a, b)(rd);
}
const int MOD = 1000000007;

long long power(long long b, int e) {
    if (e==0)
        return 1;
    long long half = power(b, e/2);
    half = (half * half) % MOD;
    if (e%2)
        return (b * half) % MOD;
    else
        return half;
}
long long inv(long long x) {
    return power(x, MOD-2);
}

struct Kranik {
    int l, r;
};

class IntervalPine {
    int epoch, start;
    vector<int> T;

    public:
        IntervalPine(int n) {
            start = 1;
            while (start < n)
                start *= 2;
            T.resize(2*start, -1);
            epoch = 0;
        }

        int get(int p) {
            p += start;
            int result = -1;
            while (p) {
                result = max(result, T[p]);
                p /= 2;
            }
            return result;
        }

        void set(int a, int b) {
            a += start;
            b += start;
            while (a <= b) {
                if (a%2 == 1)
                    T[a++] = epoch;
                if (b%2 == 0)
                    T[b--] = epoch;
                a /= 2;
                b /= 2;
            }
            epoch++;
        }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;
    vector<Kranik> K(n);
    for (Kranik& k : K)
        cin >> k.l >> k.r;

    // build DAG
    vector<int> LPl(n), LPr(n);
    IntervalPine IP(2*n+1);
    for (int i=0; i<n; i++) {
        LPl[i] = IP.get(K[i].l);
        LPr[i] = IP.get(K[i].r);
        IP.set(K[i].l, K[i].r);
    }

    // for each vertex find number of ancestors
    queue<int> Q;
    vector<int> Ancestors(n, 0);
    vector<int> FloodReasons(n, 0);
    vector<bool> Processed(n, false);
    for (int init_source=n-1; init_source>=0; init_source--) {
        if (Processed[init_source])
            continue;
        /* cerr << endl; */

        // initial flood down
        Q.push(init_source);
        while (!Q.empty()) {
            int v = Q.front();
            Q.pop();
            for (int ch : {LPl[v], LPr[v]})
                if (ch>=0)
                    if (FloodReasons[ch]++ == 0)
                        Q.push(ch);
        }

        // lowering the flood source
        FloodReasons[init_source]++;
        int counter = 0, source = init_source;

        while (source >= 0) {
            /* cerr << "SOURCE = " << source << endl; */

            // disable water at the source
            if (!Processed[source]) {
                counter++;
                Processed[source] = true;
            }
            FloodReasons[source]--;
            Q.push(source);

            // choose next source
            if (LPl[source] < 0)
                source = LPr[source];
            else if (LPr[source] < 0)
                source = LPl[source];
            else if (!Processed[LPl[source]])
                source = LPl[source];
            else if (!Processed[LPr[source]])
                source = LPr[source];
            else if (LPr[source] < LPl[source])
                source = LPl[source];
            else
                source = LPr[source];

            if (source >= 0)
                FloodReasons[source]++;

            // dry some vertices
            while (!Q.empty()) {
                int v = Q.front();
                Q.pop();
                Ancestors[v] += counter;
                /* cerr << "Adding " << counter << " ancestors to " << v << endl; */
                for (int ch : {LPl[v], LPr[v]})
                    if (ch>=0)
                        if (--FloodReasons[ch] == 0)
                            Q.push(ch);
            }
        }
    }

    // compute the result
    long long wnk_int=0, wnk_num=0, wnk_den=1;
    auto add_to_wnk = [&](long long num, long long den) {
        __int128_t new_wnk_num = (__int128_t)wnk_num*den + (__int128_t)wnk_den*num;
        __int128_t new_wnk_den = (__int128_t)wnk_den*den;
        wnk_int += new_wnk_num / new_wnk_den;
        new_wnk_num %= new_wnk_den;
        wnk_num = (long long)(new_wnk_num % MOD);
        wnk_den = (long long)(new_wnk_den % MOD);
        long long d = gcd(wnk_num, wnk_den);
        wnk_num = (wnk_num / d);
        wnk_den = (wnk_den / d);
    };

    for (int i=0; i<n; i++)
        add_to_wnk(1, Ancestors[i]);

    cout << ((wnk_num * inv(wnk_den) + wnk_int) % MOD) << '\n';
    return 0;
}