#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MN = 510;
const ll M = 1e9+7;
ll dp[2][MN*2][MN];
ll cof[MN*2][MN];
ll nv[MN],sz[2*MN];
inline ll mul(ll a, ll b) {return (a*b)%M;}
ll bp(ll b, ll p) {
ll ac = 1;
while(p) {
if(p&1) {ac = mul(ac,b);}
b = mul(b,b);
p >>= 1;
}
return ac;
}
ll inv(ll v) {return bp(v,M-2);}
void pre(int pct, int n) {
for(int i=1;i<=n+1;i++) {
nv[i] = inv(i);
}
for(int i=0;i<pct-1;i++) {
cof[i][0] = sz[i];
}
for(int i=1;i<=n;i++) {
for(int j=0;j<pct-1;j++) {
cof[j][i] = mul(cof[j][i-1],mul(sz[j]-i,nv[i+1]));
}
}
}
ll st[MN],ed[MN];
int main() {
ll n;
cin >> n;
map<ll,ll> bo;
for(int i=0;i<n;i++) {
cin >> st[i] >> ed[i];
bo[st[i]] = -1;
bo[ed[i]+1] = -1;
}
int pct = 0;
ll ls = -1;
for(auto& it: bo) {
it.second = pct;
if(pct > 0) {
sz[pct-1] = it.first-ls;
}
ls = it.first;
pct++;
}
for(int i=0;i<n;i++) {
st[i] = bo[st[i]];
ed[i] = bo[ed[i]+1];
}
pre(pct, n);
int cu = 0;
memset(dp,0,sizeof(dp));
for(int i=0;i<n;i++) {
int nu = 1-cu;
for(int j=0;j<pct-1;j++) {
for(int k=0;k<=i;k++) {
dp[nu][j][k] = dp[cu][j][k];
}
}
ll rs = 1;
for(int j=0;j<st[i];j++) {
for(int k=0;k<=i;k++) {
rs += mul(dp[cu][j][k],cof[j][k]);
if(rs >= M) {rs -= M;}
}
}
for(int j=st[i];j<ed[i];j++) {
dp[nu][j][0] += rs;
if(dp[nu][j][0] >= M) {dp[nu][j][0] -= M;}
for(int k=0;k<=i;k++) {
dp[nu][j][k+1] += dp[cu][j][k];
if(dp[nu][j][k+1] >= M) {
dp[nu][j][k+1] -= M;
}
rs += mul(dp[cu][j][k],cof[j][k]);
if(rs >= M) {rs -= M;}
}
}
cu = nu;
}
ll res = 0;
for(int i=0;i<pct-1;i++) {
for(int j=0;j<=n;j++) {
res += mul(dp[cu][i][j],cof[i][j]);
}
}
res %= M;
cout << res << '\n';
}
