#include <bits/stdc++.h>
using namespace std;
#define dbg(x) cerr << #x << ": " << x << endl;
const int MOD = 1e9 + 7;
int add(int a, int b) {
int res = a + b;
if (res >= MOD) {
res -= MOD;
}
return res;
}
int mul(long long a, int b) {
return a * b % MOD;
}
const int MAX_N = 500 + 1;
int a[MAX_N];
int b[MAX_N];
vector<int> dp[MAX_N];
struct FenwickTree {
vector<int> tree;
int size;
FenwickTree(int n) {
size = n;
tree.resize(size);
}
void update(int pos, int value) {
for (int i = pos; i < size; i |= i + 1) {
tree[i] = add(tree[i], value);
}
}
int query(int pos) {
int res = 0;
for (int i = pos; i >= 0; i = (i & (i + 1)) - 1) {
res = add(res, tree[i]);
}
return res;
}
};
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n;
cin >> n;
vector<int> as = {0};
for (int i = 1; i <= n; ++i) {
cin >> a[i] >> b[i];
for (int j = a[i]; j <= b[i]; ++j) {
as.push_back(j);
}
}
sort(as.begin(), as.end());
as.resize(unique(as.begin(), as.end()) - as.begin());
dp[0].assign(1, 1);
a[0] = -1;
b[0] = -1;
FenwickTree pref(as.size());
pref.update(0, 1);
int ans = 0;
for (int i = 1; i <= n; ++i) {
dp[i].resize(b[i] - a[i] + 1);
int m = dp[i].size();
int pos = lower_bound(as.begin(), as.end(), a[i]) - as.begin();
int pos0 = pos;
for (int j = 0; j < m; ++j) {
int x = a[i] + j;
while (as[pos] < x) ++pos;
dp[i][j] = pref.query(pos - 1);
}
for (int j = 0; j < m; ++j) {
int x = a[i] + j;
while (as[pos0] < x) ++pos0;
pref.update(pos0, dp[i][j]);
ans = add(ans, dp[i][j]);
}
}
cout << ans << '\n';
return 0;
}
/*
*/
