Submission #1627253

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Source Code Expand

#include <iostream>
#include <deque>
using namespace std;

int main(){
	int64_t n, k;
	cin >> n >> k;
	deque<int64_t> dq(k, 0);
	dq[1] = 1;
	int64_t sum = 1, mod = 1e9 + 7;
	for(int i = 0; i < n - 2; i++){
		dq.emplace_front(sum);
		sum *= 2;
		sum -= dq.back();
		sum += mod;
		sum %= mod;
		dq.pop_back();
	}
	{
		sum -= dq.back();
		sum += mod;
		sum %= mod;
		dq.pop_back();
	}
	cout << sum << endl;
}

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