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47 lines
895 B
C++
47 lines
895 B
C++
#include <iostream>
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#include <algorithm>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 6005;
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const int mod = 1e9 + 7;
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int n, f[N][2], ans;
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std::pair<int, int> a[N];
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n;
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for (int i = 1; i <= n; i++) {
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cin >> a[i].first >> a[i].second;
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}
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std::sort(a + 1, a + 1 + n);
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f[1][0] = f[1][1] = 1;
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for (int i = 2; i <= n; i++) {
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f[i][0] = f[i][1] = 1;
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for (int j = i - 1; j; j--) {
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if (a[j].second > a[i].second) {
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f[j][1] = (f[j][1] + f[i][0]) % mod;
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} else {
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f[i][0] = (f[i][0] + f[j][1]) % mod;
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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ans = (static_cast<long long>(ans) + f[i][0] + f[i][1] - 1) % mod;
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}
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cout << ans << endl;
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return 0;
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}
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