Submission #19010

#	TimeUTC-0	Username	Problem	Language	Result	Execution time	Memory
19010	2016-02-17 02:58:23	kriii	팔찌 (kriii4_V)	C++14	100 / 100	121 ms	32332 KiB

V

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#include <stdio.h>
const long long mod = 1000000007;
const long long inv2 = 500000004;
long long inv[1000001],kpow[1000001],phi[1000001],syn[1000001];
int main()
{
  int N,K;
  scanf ("%d %d",&N,&K);
  
  inv[1] = 1;
  for (int i=2;i<=N;i++) inv[i] = (mod - mod / i) * inv[mod % i] % mod;
  kpow[0] = 1;
  for (int i=1;i<=N;i++) kpow[i] = kpow[i-1] * K % mod;
  for (int i=1;i<=N;i++){
    phi[i] += i;
    for (int j=i*2;j<=N;j+=i) phi[j] -= phi[i];
  }
  for (int i=1;i<=N;i++){
    syn[i] = (syn[i-1] + kpow[i] * inv[i]) % mod;
  }
  long long ans = 2;
  for (int i=1;i<=N;i++){
    ans = (ans + phi[i] * syn[N/i] % mod * inv[i] % mod) % mod;
 
 
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• Subtask 1: 6 / 6
• Subtask 2: 94 / 94