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

const int64_t MOD = 1e9+7;
void add(int64_t& a, int64_t b){
    a = (a+b) % MOD;
}
void mul(int64_t& a, int64_t b){
    a = a*b % MOD;
}

vector<int64_t> fact, seq_inv, fact_inv;

void create_fact_mod(int num){
    fact[0] = fact[1] = 1;
    for(int i=2; i<=num; i++) fact[i] = fact[i-1] * i % MOD;
}

void create_seq_inv_mod(int num){
    seq_inv[0] = seq_inv[1] = 1;
    for(int i=2; i<=num; i++) seq_inv[i] = (MOD - MOD/i) * seq_inv[MOD%i] % MOD;
}

void create_fact_inv_mod(int num){
    fact_inv[0] = fact_inv[1] = 1;
    for(int i=2; i<=num; i++) fact_inv[i] = fact_inv[i-1] * seq_inv[i] % MOD;
}

void create_mod_tables(int num){
    fact.resize(num+1);
    seq_inv.resize(num+1);
    fact_inv.resize(num+1);
    create_fact_mod(num);
    create_seq_inv_mod(num);
    create_fact_inv_mod(num);
}

int64_t comb_mod(int n, int k){
    return fact[n] * fact_inv[n-k] % MOD * fact_inv[k] % MOD;
}

int64_t perm_mod(int n, int k){
    return fact[n] * fact_inv[n-k] % MOD;
}

int64_t power_mod(int64_t num, int64_t power){
    int64_t prod = 1;
    num %= MOD;
    while(power > 0){
        if(power&1) prod = prod * num % MOD;
        num = num * num % MOD;
        power >>= 1;
    }
    return prod;
}

int64_t extgcd(int64_t a, int64_t b, int64_t& x, int64_t& y){
    int64_t d = a;
    if(b != 0){
        d = extgcd(b, a%b, y, x);
        y -= (a/b) * x;
    }else{
        x = 1; y = 0;
    }
    return d;
}

int64_t inv_mod(int64_t a){
    int64_t x, y;
    extgcd(a, MOD, x, y);
    return (MOD + x%MOD) % MOD;
}

int main(){
    int N, A[201], B[201];
    map<int, int> mp;
    cin >> N;
    for(int i=0; i<N; i++){
        cin >> A[i] >> B[i];
        mp[A[i]] = mp[B[i]] = 0;
    }
    int sz = 0;
    vector<int> cmp;
    for(auto p : mp){
        mp[p.first] = sz++;
        cmp.push_back(p.first);
    }
    A[N] = B[N] = (N%2 ? cmp[sz-1] : cmp[0]);
    create_mod_tables(N);
    int64_t sub[201] = {0}, fact[201] = {0};
    sub[0] = sub[1] = fact[1] = 1;
    for(int i=2; i<=N; i++){
        for(int j=0; i-j-1>=0; j+=2) add(sub[i], sub[j] * sub[i-j-1] % MOD * comb_mod(i-1, j));
        fact[i] = fact[i-1] * i % MOD;
    }
    for(int i=2; i<=N; i++) mul(sub[i], inv_mod(fact[i]));


    int64_t dp[201][401] = {0};
    for(int j=0; j<sz; j++) if(A[0] <= cmp[j] && cmp[j] <= B[0]) dp[0][j] = 1;
    for(int i=0; i<N; i++){
        int64_t sum = 0;
        if(i%2 == 0){
            for(int j=0; j<sz; j++){
                if(A[i+1] <= cmp[j] && cmp[j] <= B[i+1]) add(dp[i+1][j], sum);
                int64_t res = 0;
                int64_t C = 1;
                for(int k=i; k>=0; k--){
                    if(j<sz-1 && A[k] <= cmp[j] && cmp[j+1] <= B[k]){
                        mul(C, (cmp[j+1] - cmp[j]) * inv_mod(B[k] - A[k]) % MOD);
                        add(res, dp[k][j + (k%2 == 0)] * C % MOD * sub[i-k+1]);
                    }else{
                        break;
                    }
                }
                add(sum, res);
            }
        }else{
            for(int j=sz-1; j>=0; j--){
                int64_t res = 0;
                int64_t C = 1;
                for(int k=i; k>=0; k--){
                    if(j<sz-1 && A[k] <= cmp[j] && cmp[j+1] <= B[k]){
                        mul(C, (cmp[j+1] - cmp[j]) * inv_mod(B[k] - A[k]) % MOD);
                        add(res, dp[k][j + (k%2 == 0)] * C % MOD * sub[i-k+1]);
                    }else{
                        break;
                    }
                }
                add(sum, res);
                if(A[i+1] <= cmp[j] && cmp[j] <= B[i+1]) add(dp[i+1][j], sum);
            }
        }
    }
    int64_t ans = (N%2 ? dp[N][sz-1] : dp[N][0]);
    cout << ans << endl;
}