Submission #22,233

2026-01-14 18:18:24

cpp17

Accepted 50/50

8ms

2600 KiB

#include <bits/stdc++.h>
using namespace std;

#define int int64_t

int p(int a , int b , int m){
	int x = 1;
	for(int i = 0; i < 30; i++){
		if((1<<i)&b){
			x*=a;
			x%=m;
		}
		a*=a;
		a%=m;
	}
	return x;
}

int M = 1e9+7;

vector<int> f;

int32_t main() {
	int b , c;cin >> b >> c;
	f.push_back(1);
	for(int i = 1; i <= 2*c; i++){
		f.push_back((f.back()*i)%M);
	}
	int d = (f[c-1+c-b]*p((f[c-1]*f[c-b])%M , M-2 , M))%M;
	int e = (f[c-1+c-b]*p((f[c]*f[c-b-1])%M , M-2 , M))%M;
	cout << (d-e+M*3)%M << endl;
}

	Sum	Test	Verdict		Time	Memory
base	50/50
		1	Accepted	0/0	1ms	316 KiB
		2	Accepted	0/0	1ms	316 KiB
		3	Accepted	2/2	1ms	316 KiB
		4	Accepted	3/3	1ms	564 KiB
		5	Accepted	3/3	1ms	316 KiB
		6	Accepted	3/3	1ms	316 KiB
		7	Accepted	3/3	1ms	316 KiB
		8	Accepted	3/3	1ms	400 KiB
		9	Accepted	3/3	2ms	556 KiB
		10	Accepted	3/3	1ms	316 KiB
		11	Accepted	3/3	1ms	568 KiB
		12	Accepted	3/3	2ms	624 KiB
		13	Accepted	3/3	2ms	988 KiB
		14	Accepted	3/3	7ms	2468 KiB
		15	Accepted	3/3	4ms	1452 KiB
		16	Accepted	3/3	8ms	2468 KiB
		17	Accepted	3/3	4ms	1452 KiB
		18	Accepted	3/3	7ms	2600 KiB
		19	Accepted	3/3	8ms	2544 KiB