#include<bits/stdc++.h>
// #include<atcoder/modint>
// #include<atcoder/convolution>
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define F first
#define S second
#define rs resize
#define ft front()
#define bk back()
#define int long long
#define vi vector<int>
#define vvi vector<vector<int>>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>
#define vc vector<char>
#define vb vector<bool>
#define mii map<int,int>
#define f0r(i,n) for(int i=0;i<n;i++)
#define FOR(i,k,n) for(int i=k;i<n;i++)
#define r0f(i,n) for(int i = n-1; i >= 0; i--)
#define R0F(i,k,n) for(int i = n-1; i >= k; i--)
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define SUM(v) (accumulate(all(v), 0LL))
#define in(a) int a; cin>>a
#define in2(a,b) int a,b; cin>>a>>b
#define in3(a,b,c) int a,b,c; cin>>a>>b>>c
#define in4(a,b,c,d) int a,b,c,d; cin>>a>>b>>c>>d
#define vin(v,n); vi v(n); f0r(i,n){cin>>v[i];}
#define out(a) cout<<a<<'\n'
#define out2(a,b) cout<<a<<' '<<b<<'\n'
#define out3(a,b,c) cout<<a<<' '<<b<<' '<<c<<'\n'
#define out4(a,b,c,d) cout<<a<<' '<<b<<' '<<c<<' '<<d<<'\n'
#define pout(a) cout<<a.first<<' '<<a.second<<'\n'
#define vout(v) for(auto u : v){cout<<u<<' ';} cout<<endl
#define dout(a) cout<<a<<' '<<#a<<endl
#define dout2(a,b) cout<<a<<' '<<#a<<' '<<b<<' '<<#b<<endl
#define YN(x); if(x){cout<<"YES"<<'\n';}else{cout<<"NO"<<'\n';}
#define yn(x); if(x){cout<<"Yes"<<'\n';}else{cout<<"No"<<'\n';}
#define p2(x) (1LL << (x))
#define pct(x) (__builtin_popcountll((x)))
#define ist(x,y) (((x) >> (y)) & 1)
#define sz(x) (int)((x).size())
template<class T, class U> bool ckmin(T& a, const U& b) { return (T)b < a ? a = (T)b, 1 : 0; }
template<class T, class U> bool ckmax(T& a, const U& b) { return a < (T)b ? a = (T)b, 1 : 0; }
const int leg = 1e9 + 7;
const int mod = leg;
using namespace std;
const int mxn = 2005;
int inv[2005];
int binexp(int a, int b){
int ret = 1; f0r(i,30){
if(ist(b,i))ret *= a, ret %= mod; a *= a, a %= mod;
} return ret;
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
//ifstream cin(".in");
//ofstream cout(".out");
// fact[0]=1;FOR(i,1,mxn)fact[i]=fact[i-1]*i;inv[mxn-1]=fact[mxn-1].inv();r0f(i,mxn-1)inv[i]=inv[i+1]*(i+1);
f0r(i,mxn)inv[i]=binexp(i,mod-2);
in(n); vi l(n), r(n); set<int>s; f0r(i,n)cin>>l[i]>>r[i],s.insert(l[i]-1),s.insert(r[i]);
vpii segs; int pv = 0; for(auto u : s)segs.eb(pv, u), pv = u+1; int m = segs.size(); //dout(m);
// for(auto [a,b] : segs)dout2(a,b);
vvi f(m, vi(n+1)); vi g(m); f0r(i,n){
int x, y; f0r(j, m)if(segs[j].F == l[i]){x=j; break;} r0f(j,m)if(segs[j].S == r[i]){y=j; break;}
int sum = 0; f0r(j,x)sum += g[j], sum %= mod; FOR(j,x,y+1){
for(int k = n; k >= 1; k--)f[j][k] = f[j][k] + f[j][k-1], f[j][k] %= mod; f[j][0] += sum+1, f[j][0] %= mod;
sum += g[j], sum %= mod;
}
FOR(j,x,y+1){
int L = segs[j].S - segs[j].F, mult = L+1, ptr = L;
int cur = 0; f0r(k,n+1){
cur += f[j][k] * mult % mod; mult *= ptr, mult %= mod, mult *= inv[L+2-ptr], mult %= mod; if(ptr==0)break;
} g[j] = cur;
} //vout(f[2]); vout(g);
}
int ans = 0; f0r(i,m)ans+=g[i],ans%=mod; out(ans);
}
