Submission #2852446

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Source Code Expand

#include <iostream>
#include <vector>
#include <utility>
#include <algorithm>
#define llint long long 
#define mod 1000000007

using namespace std;

llint n;
vector< pair<llint, llint> > vec;

int main(void)
{
	cin >> n;
	llint a;
	for(int i = 0; i < n; i++){
		cin >> a;
		vec.push_back(make_pair(a, 1));
	}
	for(int i = 0; i < n; i++){
		cin >> a;
		vec.push_back(make_pair(a, -1));
	}
	sort(vec.begin(), vec.end());
	
	llint ans = 1, stk = 0;
	for(int i = 0; i < vec.size(); i++){
		if(vec[i].second > 0){
			if(stk < 0) ans *= -stk;
			stk++;
		}
		else{
			if(stk > 0) ans *= stk;
			stk--;
		}
		ans %= mod;
	}
	cout << ans << endl;
	return 0;
}

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