#pragma GCC optimize("O3,unroll-loops")
#include <bits/stdc++.h>
using namespace std;
using ll = long long; using pii = pair<ll,ll>;
ll ans = 0;
const ll p = 1e9+7;
const ll Nm = 505;
ll vinv[Nm];
struct Node {
ll l,r; //left, right
bool isS; //is short (aka length 1)
ll lmx = 0;
vector<ll> velem; //length-Nm vector of elements
vector<ll> vbin;
ll nv; //node value
Node(){}
Node(ll l0, ll r0) {
l = l0; r = r0;
if (l==r) {
isS = 1;
nv = 0;
} else {
isS = 0;
velem = vbin = vector<ll>(Nm,0);
lmx = 1;
nv = 0;
vbin[0]=r-l+1;
for (ll i=1;i<(Nm-1);i++) {
vbin[i]=(vbin[i-1]*vinv[i+1])%p;
vbin[i]=(vbin[i]*(r-l+1-i))%p;
}
}
}
void incS() {
if (isS) {
return;
}
vector<ll> vel2 = vector<ll>(Nm,0);
for (ll i=0;i<lmx;i++) {
if (velem[i]>0) {
vel2[i]=(vel2[i]+velem[i])%p;
vel2[i+1]=(vel2[i+1]+velem[i])%p;
}
}
lmx++;
velem=vel2;
ll nvf = 0;
for (ll i=0;i<lmx;i++) {
nvf = (nvf+velem[i]*vbin[i])%p;
}
nv=nvf;
}
void incV(ll ev) {
nv = (nv+(r-l+1)*ev)%p;
if (!isS) {
velem[0]=(velem[0]+ev)%p;
}
}
};
vector<Node> vecN;
ll inv(ll x) {
array<ll,3> a = {x,1,0};
array<ll,3> b = {p,0,1};
while (a[0]!=0) {
if (a[0]>b[0]) {
swap(a,b);
} else {
ll k = b[0]/a[0];
for (ll i=0;i<3;i++) {
b[i]-=k*a[i];
}
}
}
ll fvb = b[1];
return (fvb+(2-fvb/p)*p)%p;
}
int main() {
for (ll i=1;i<Nm;i++) {
vinv[i]=inv(i);
}
ll N; cin >> N;
vector<pii> vupd;
vector<ll> vdel = vector<ll>(1,0);
for (int i=0;i<1;i++) {
vdel[i]=i;
}
ll bmax = -1;
for (ll n=0;n<N;n++) {
ll a,b; cin >> a >> b;
bmax = max(b,bmax);
vupd.push_back({a,b});
for (ll d=0;d<=0;d++) {
vdel.push_back(a+d);
vdel.push_back(b+1+d);
}
}
sort(vdel.begin(),vdel.end());
vdel.erase(unique(vdel.begin(),vdel.end()),vdel.end());
vector<ll> vdel2;
for (ll x: vdel) {
if (x<=(bmax+1)) {
vdel2.push_back(x);
}
}
vdel2 = vdel;
for (ll x=0;x<(ll)(vdel2.size()-1);x++) {
vecN.push_back(Node(vdel2[x],vdel2[x+1]-1));
//associated with [vdel2[x],vdel2[x+1])
}
vecN[0].incV(1);
for (pii pupd: vupd) {
ll a = pupd.first; ll b = pupd.second; //update [a,b+1)
ll rtot = 0;
for (ll i=0;i<vecN.size();i++) {
ll vnl = vecN[i].l; ll vnr = vecN[i].r;
ll rnew = vecN[i].nv;
if (a<=vnl && vnr<=b) {
vecN[i].incS();
vecN[i].incV(rtot);
rtot = (rtot+rnew)%p;
} else {
rtot = (rtot+rnew)%p;
}
//cout << "rtot="<<rtot<<"\n";
}
}
for (ll i=0;i<vecN.size();i++) {
ans = (ans+vecN[i].nv)%p;
}
ans = (ans+p-1)%p;
cout << ans << "\n";
}
