#include <bits/stdc++.h>
#pragma GCC optimize ("O2")
#pragma GCC optimize ("unroll-loops")
//#pragma GCC optimize("no-stack-protector,fast-math")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr<<#x<<'='<<(x)<<endl;
#define debugp(x) cerr<<#x<<"= {"<<(x.first)<<", "<<(x.second)<<"}"<<endl;
#define debug2(x, y) cerr<<"{"<<#x<<", "<<#y<<"} = {"<<(x)<<", "<<(y)<<"}"<<endl;
#define debugv(v) cerr<<#v<<" : ";for (auto x:v) cerr<<x<<' ';cerr<<endl;
#define all(x) x.begin(), x.end()
#define pb push_back
#define kill(x) return cout<<x<<'\n', 0;
const ld eps=1e-7;
const int inf=1000000010;
const ll INF=10000000000000010LL;
const int mod = 1000000007;
const int MAXN = 510, LOG=20;
ll n, m, k, u, v, x, y, t, a, b, ans;
int A[MAXN], B[MAXN];
int dp[2][MAXN*2][MAXN];
ll F[MAXN], I[MAXN];
ll ent[MAXN*2][MAXN];
vector<int> comp;
ll powmod(ll a, ll b){
ll res=1;
for (; b; b>>=1, a=a*a%mod) if (b&1) res=res*a%mod;
return res;
}
int C(int n, int r){
if (r<0 || r>n) return 0;
ll res=1;
for (int i=n; i>n-r; i--) res=res*i%mod;
return res*I[r]%mod;
}
inline void _add(int &x, int y){
x+=y;
if (x>=mod) x-=mod;
}
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
F[0]=1;
for (int i=1; i<MAXN; i++) F[i]=F[i-1]*i%mod;
I[MAXN-1]=powmod(F[MAXN-1], mod-2);
for (int i=MAXN-1; i; i--) I[i-1]=I[i]*i%mod;
cin>>n;
for (int i=1; i<=n; i++){
cin>>A[i]>>B[i];
comp.pb(A[i]);
comp.pb(++B[i]);
}
comp.pb(0);
sort(all(comp));
comp.resize(unique(all(comp))-comp.begin());
m=comp.size()-1;
for (int i=0; i<m; i++) for (int j=0; j<=n; j++) ent[i][j]=C(comp[i+1]-comp[i], j);
for (int i=1; i<=n; i++){
A[i]=lower_bound(all(comp), A[i])-comp.begin();
B[i]=lower_bound(all(comp), B[i])-comp.begin();
}
dp[0][0][0]=1;
int prev=0, curr=1;
for (int i=1; i<=n; i++){
memset(dp[curr], 0, sizeof(dp[curr]));
dp[curr][0][0]=1;
for (int j=1; j<=m; j++){
for (int k=1; k<=i; k++){
dp[curr][j][k]=dp[prev][j][k];
if (A[i]<=j && j<B[i]){
if (k>1) _add(dp[curr][j][k], dp[prev][j][k-1]);
else for (int jj=0; jj<j; jj++) _add(dp[curr][j][k], dp[prev][jj][0]);
}
}
for (int kk=1; kk<=i; kk++) dp[curr][j][0]=(dp[curr][j][0]+dp[curr][j][kk]*ent[j][kk])%mod;
}
swap(prev, curr);
}
for (int j=1; j<=m; j++) ans=(ans+dp[prev][j][0])%mod;
cout<<ans<<'\n';
return 0;
}
