BZOJ 2190 仪仗队

#include<stdio.h>#include<string.h>#include<stdlib.h>#include<algorithm>#include<iostream>#include<vector>#include<stack>#include<queue>using namespace std;int N;long long phi(int x){      long long ans=x;      for(int i=2;i*i<=x;i++)      {            if(!(x%i))            {                  ans=ans/i*(i-1);                  while(!(x%i)) x/=i;            }      }      if(x>1)   ans=ans/x*(x-1);      return ans;}int main(){      //freopen("input.in","r",stdin);  //freopen("output.out","w",stdout);   scanf("%d",&N);  long long ans=2;  for(int i=2;i<N;i++)        ans+=phi(i);      printf("%lld\n",2*ans-1);  //system("pause");      return 0;}