제출 #894312

#제출 시각아이디문제언어결과실행 시간메모리
894312vjudge1Rack (eJOI19_rack)C++11
100 / 100
14 ms448 KiB
#include <bits/stdc++.h>
#define pb push_back
#define pf push_front
using namespace std;
#define F first
#define S second
typedef long long ll;
#define pii pair <int, int>
#define pll pair <ll, ll>
typedef long double ld;
const ll N = 1e5 + 10;
const ll mod = 1e9 + 7;

ll um(ll a, ll b){
	return ((1LL * a * b) % mod + mod) % mod;
}
ll subr(ll a, ll b){
	return ((1LL * a - b) % mod + mod) % mod;
}
ll add(ll a, ll b){
	return ((1LL * a + b) % mod + mod) % mod;
}
ll binpow(ll x, ll step){
	ll res = 1LL;
	while(step){
		if(step & 1) res = um(res, x);
		x = um(x, x);
		step /= 2;
	}
	return res;
}
/*
	Восемь восемьсот пять пять пять
	три пять три пять
	Проще кому то позвонить
	чем у кого-то деньги занимать
*/
int main() {
	ios::sync_with_stdio(false);
  	cin.tie(NULL);
  	ll n, k, ans = 1LL, num = 1LL;
  	cin >> n >> k;
  	for(ll i = 0; i < n - 1; i++){
  		ans = um(ans, 2LL);
  	}
  	ll rev2 = binpow(2LL, mod - 2);
  	for(ll i = 0; i < n; i++){
  		if(k % 2 == 0) num = add(num, ans);
  		k = (k + 1) / 2;
  		ans = um(ans, rev2);
  	}
  	cout << num;
  return 0;
}
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