【CSRound#48(Div.2only)】DominantFreeSets

#include 
using namespace std;


const int N = 1e5;
const long long MOD = 1e9 + 7;


struct BI {
	long long a[N + 10];


	int lowbit(int x) {
		return x&(-x);
	}


	void add(int x, long long y) {
		while (x <= N) {
			a[x] = ((a[x] + y) % MOD + MOD) % MOD;
			x += lowbit(x);
		}
	}


	long long sum(int x) {
		long long now = 0;
		while (x > 0) {
			now = ((now + a[x]) % MOD + MOD) % MOD;
			x -= lowbit(x);
		}
		return now;
	}


	long long get_sum(int l, int r) {
		return sum(r) - sum(l - 1);
	}


}b;


vector  > v;
int n;
long long sum = 0, ans = 0;


int main() {
	//freopen("F:\\rush.txt", "r", stdin);
	ios::sync_with_stdio(0), cin.tie(0);
	cin >> n;
	for (int i = 1, x, y; i <= n; i++) {
		cin >> x >> y;
		v.push_back(make_pair(x, y));
	}
	sort(v.begin(), v.end());
	b.add(v[0].second, 1);
	int j = 1;
	sum = 1;
	while (j <= (int)v.size() - 1 && v[j].first == v[0].first) {
		b.add(v[j].second, 1);
		sum += 1;
		j++;
	}
	ans = n;
	for (int i = j; i <= n - 1; i++) {
		long long temp = b.get_sum(1, v[i].second);
		long long temp1 = ((sum - temp) % MOD + MOD) % MOD;
		b.add(v[i].second, (temp1 + 1) % MOD);
		ans = (ans + temp1) % MOD;
		sum = (sum + temp1 + 1) % MOD;
	}
	cout <