#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef __int128 lll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<ld, ld> pld;
#define MAX 9223372036854775807LL
#define MIN -9223372036854775807LL
#define INF 0x3f3f3f3f3f3f3f3f
#define fi first
#define se second
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); cout << fixed; cout.precision(10);
#define sp << " "
#define en << "\n"
#define compress(v) sort(v.begin(), v.end()), v.erase(unique(v.begin(), v.end()), v.end())
ll n;
pll a[1010];
ll ss = 1000000007;
ll inv[1010];
vector<ll> zip;
ll dp[1010][1010];
ll sum[1010][1010];
ll LC[1010];
ll xjc[1010];
ll sqrmtp(ll X, ll Y)
{
ll ret = 1;
while(Y)
{
if(Y & 1)
ret = ret * X % ss;
X = X * X % ss;
Y >>= 1;
}
return ret;
}
int main(void)
{
fastio
cin >> n;
for(ll i = 1 ; i <= n ; i++)
{
cin >> a[i].fi >> a[i].se;
zip.push_back(a[i].fi);
zip.push_back(a[i].se + 1);
}
for(ll i = 1 ; i <= n ; i++)
inv[i] = sqrmtp(i, ss - 2);
compress(zip);
dp[0][0] = 1;
sum[0][0] = 1;
for(ll i = 1 ; i <= n ; i++)
sum[0][i] = 1;
ll siz = (ll)zip.size();
for(ll i = 1 ; i < siz ; i++)
{
vector<ll> num;
for(ll j = 1 ; j <= n ; j++)
{
if(a[j].fi <= zip[i - 1] && zip[i] - 1 <= a[j].se)
num.push_back(j);
}
ll L = zip[i] - zip[i - 1];
LC[0] = 1;
for(ll j = 1 ; j <= n ; j++)
{
if(L <= 0)
break;
LC[j] = LC[j - 1] * L % ss * inv[j] % ss;
L--;
}
L = zip[i] - zip[i - 1];
ll siz2 = (ll)num.size();
for(ll j = 0 ; j <= siz2 ; j++)
{
ll gap = j;
ll gap2 = 1;
xjc[j] = 0;
if(L <= 1)
continue;
xjc[j] = LC[2];
for(ll k = 1 ; ; k++)
{
if(k + 2 > L || k > j)
break;
gap2 = gap2 * gap % ss * inv[k] % ss;
gap--;
xjc[j] = (xjc[j] + gap2 * LC[k + 2] % ss) % ss;
}
}
for(ll j = 0 ; j < siz2 ; j++)
{
dp[i][num[j]] = (dp[i][num[j]] + sum[i - 1][num[j] - 1] * LC[1] % ss) % ss;
if(L >= 2)
{
for(ll k = 0 ; k < j ; k++)
dp[i][num[j]] = (dp[i][num[j]] + sum[i - 1][num[k] - 1] * xjc[j - k - 1] % ss) % ss;
}
}
for(ll j = 0 ; j <= n ; j++)
dp[i][j] = (dp[i][j] + dp[i - 1][j]) % ss;
sum[i][0] = dp[i][0];
for(ll j = 1 ; j <= n ; j++)
sum[i][j] = (sum[i][j - 1] + dp[i][j]) % ss;
}
sum[siz - 1][n]--;
sum[siz - 1][n] = (sum[siz - 1][n] % ss + ss) % ss;
cout << sum[siz - 1][n];
return 0;
}
