#include<bits/stdc++.h>
using namespace std;
#define ub upper_bound
const int nax = 503;
const int mod = 1e9 + 7;
const int cax = 1e6 + 3;
const long long sux = 103217;
vector<int>ind[nax*2];
int a[nax], b[nax];
int n, m;
int dp[nax*2][nax];
int inv[nax];
int fac[nax], iv[nax];
vector<int>imp;
int add(int a, int b) {
a += b;
if(a>=mod) a -= mod;
return a;
}
int mul(int a, int b) {
return (a * 1LL * b) % mod;
}
int quickpow(int a, int b) {
int ret = 1;
while(b) {
if(b&1) ret = mul(ret, a);
a = mul(a, a);
b >>= 1;
}
return ret;
}
vector<pair<long long,int>>table[cax];
int C(int n, int r) {
if(n<nax) {
return mul(fac[n], mul(iv[r], iv[n-r]));
}
long long H = n * sux + r;
int H2 = H % cax;
for(auto x : table[H2]) {
if(x.first==H) return x.second;
}
int ret = 1;
for(int i=n-r+1; i<=n; ++i) {
ret = mul(ret, i);
}
for(int i=1; i<=r; ++i) {
ret = mul(ret, inv[i]);
}
table[H2].emplace_back(H, ret);
return ret;
}
vector<pair<long long,int>>andp[cax];
int get(int len, int op) {
long long H = len * sux + op;
int H2 = H % cax;
for(auto x : andp[H2]) {
if(x.first==H) return x.second;
}
int ret = 0;
for(int take=0, to=min(op, len-1); take<=to; ++take) {
ret = add(ret, mul(C(op, take), C(len, take+1)));
}
andp[H2].emplace_back(H, ret);
return ret;
}
int solve(int i, int prv) {
if(i==m-1) return prv>0;
int &ret = dp[i][prv];
if(ret!=-1) return ret;
ret = 0;
ret = solve(i+1, prv);
int len = imp[i+1]-imp[i];
for(int mx=ub(ind[i].begin(), ind[i].end(), prv)-ind[i].begin(),
cur_op=0, sz=ind[i].size(); mx<sz; ++mx, ++cur_op) {
if(ind[i][mx]<=prv) continue;
int cur = mul(solve(i+1, ind[i][mx]), get(len, cur_op));
ret = add(ret, cur);
}
return ret;
}
void PlayGround() {
cin>>n;
set<int>pts;
for(int i=1; i<=n; ++i) {
cin>>a[i]>>b[i];
pts.insert(a[i]);
pts.insert(b[i]+1);
}
for(int x : pts) {
imp.push_back(x);
}
m = imp.size();
for(int i=0; i<m; ++i) {
for(int j=1; j<=n; ++j) {
if(imp[i]>=a[j] && imp[i]<=b[j]) {
ind[i].push_back(j);
}
}
}
for(int i=1; i<nax; ++i) {
inv[i] = quickpow(i, mod-2);
}
fac[0] = iv[0] = 1;
for(int i=1; i<nax; ++i) {
fac[i] = mul(i, fac[i-1]);
iv[i] = mul(iv[i-1], inv[i]);
}
memset(dp, -1, sizeof dp);
cout<<solve(0, 0)<<'\n';
// cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
PlayGround();
return 0;
}
