This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int md = (int)1e9 + 7;
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
int n;
cin >> n;
vector<int> a(n), b(n);
for (int i = 0; i < n; i++) cin >> a[i] >> b[i];
map<int, int> m;
for (int i = 0; i < n; i++) {
// cout << "\ni " << i << '\n';
int x = (m.empty() || a[i] <= (*m.begin()).first ? 0 : (*--m.lower_bound(a[i])).second);
if (m.find(a[i]) == m.end()) m[a[i]] = x;
for (int j = a[i] + 1; j <= b[i]; j++) {
if (m.find(j) == m.end()) m[j] = m[j - 1];
}
int sm = 0;
for (int j = a[i]; j <= b[i]; j++) {
int y = m[j];
sm = (sm + x + 1) % md;
m[j] = (m[j] + x + 1) % md;
// cout << "j " << j << ' ' << y << ' ' << m[j] << ' ' << x << '\n';
x = y;
}
auto t = m.upper_bound(b[i]);
while (t != m.end()) {
m[(*t).first] = (m[(*t).first] + sm) % md;
t++;
}
}
cout << (*--m.end()).second << '\n';
// int sm = 0;
// for (auto i : m) sm = (sm + i.second) % md;
// cout << sm << '\n';
}
/*sub1
vector<int> dp(n);
for (int i = 0; i < n; i++) {
dp[i] = 1;
for (int j = 0; j < i; j++) {
if (a[j] < a[i]) dp[i] = (dp[i] + dp[j]) % md;
}
}
int sm = 0;
for (auto i : dp) sm = (sm + i) % md;
cout << sm;
*/
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