#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MOD = 1e9 + 7;
ll modpow(ll a, ll e) {
ll r = 1;
while (e) {
if (e & 1) r = r * a % MOD;
a = a * a % MOD;
e >>= 1;
}
return r;
}
void addmod(int &x, int y) {
x += y;
if (x >= MOD) x -= MOD;
}
int mulmod(int a, int b) { return (int)((1LL * a * b) % MOD); }
int dp[2][1005][505];
int n;
int a[505], b[505];
int sz[1005];
long long sz1[1005];
int Ctab[1005][505];
int tot[1005];
vector<long long> comp;
ll inv_int[505];
ll comb_large(ll G, int k) {
if (k < 0) return 0;
if (k == 0) return 1;
if (G < k) return 0;
ll res = 1;
for (int i = 1; i <= k; ++i) {
ll num = (G - i + 1) % MOD;
if (num < 0) num += MOD;
res = (res * num) % MOD;
res = (res * inv_int[i]) % MOD;
}
return res;
}
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
if (!(cin >> n)) return 0;
comp.clear();
for (int i = 1; i <= n; ++i) {
cin >> a[i] >> b[i];
comp.push_back(a[i]);
comp.push_back((long long)b[i] + 1);
}
comp.push_back(0);
sort(comp.begin(), comp.end());
comp.erase(unique(comp.begin(), comp.end()), comp.end());
int M = (int)comp.size() - 1;
for (int i = 0; i <= M; ++i) {
if (i < M) {
ll G = comp[i+1] - comp[i];
sz1[i] = G;
sz[i] = (int)min<ll>(G, n);
} else {
sz1[i] = 1;
sz[i] = 1;
}
}
inv_int[0] = 0;
for (int i = 1; i <= n; ++i) inv_int[i] = modpow(i, MOD - 2);
for (int i = 0; i <= M; ++i) {
Ctab[i][0] = 1;
for (int len = 1; len <= sz[i]; ++len) {
Ctab[i][len] = (int)comb_large(sz1[i], len);
}
}
memset(dp, 0, sizeof(dp));
dp[0][0][0] = 1;
for (int i = 1; i <= n; ++i) {
int cur = i & 1;
int prv = cur ^ 1;
for (int j = 0; j <= M; ++j) for (int len = 0; len <= sz[j]; ++len) dp[cur][j][len] = 0;
for (int j = 0; j <= M; ++j) {
for (int len = 0; len <= sz[j]; ++len) {
if (dp[prv][j][len]) addmod(dp[cur][j][len], dp[prv][j][len]);
}
}
int L = int(lower_bound(comp.begin(), comp.end(), a[i]) - comp.begin());
int R = int(lower_bound(comp.begin(), comp.end(), (long long)b[i] + 1) - comp.begin() - 1);
if (R < L) {
continue;
}
for (int t = 0; t <= R; ++t) tot[t] = 0;
for (int k = 0; k <= R; ++k) {
if (k > 0) tot[k] = tot[k-1];
else tot[k] = 0;
for (int len = 0; len <= sz[k]; ++len) {
if (dp[prv][k][len] == 0) continue;
addmod(tot[k], mulmod(dp[prv][k][len], Ctab[k][len]));
}
}
for (int j = L; j <= R; ++j) {
for (int len = 0; len < sz[j]; ++len) {
if (dp[prv][j][len] == 0) continue;
addmod(dp[cur][j][len+1], dp[prv][j][len]);
}
int prev_tot = (j == 0 ? 0 : tot[j-1]);
if (prev_tot) addmod(dp[cur][j][1], prev_tot);
}
for (int j = 0; j <= M; ++j) for (int len = 0; len <= sz[j]; ++len) dp[prv][j][len] = 0;
}
int ans = 0;
int last = n & 1;
for (int j = 0; j <= M; ++j) {
for (int len = 0; len <= sz[j]; ++len) {
if (dp[last][j][len] == 0) continue;
addmod(ans, mulmod(dp[last][j][len], Ctab[j][len]));
}
}
ans = (ans - 1) % MOD;
if (ans < 0) ans += MOD;
cout << ans << '\n';
return 0;
}
