OJ-Problems-Source/HDOJ/2866_autoAC.cpp

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#include <cstring>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <cstdio>
using namespace std;
#define maxn 1000010
bool prime[maxn];
void Prime()
{
memset(prime,true,sizeof(prime));
prime[0]=prime[1]=0;
for(int i=2;i*i<maxn;i++)
if(prime[i])
for(int j=2*i;j<maxn;j+=i)
prime[j]=0;
}
int main()
{
Prime();
int n,ans,p;
while(scanf("%d",&n)!=EOF)
{
ans=0;
for(int i=1;;i++)
{
int tmp=3*i*i+3*i+1;
if(tmp>n)
break;
if(prime[tmp])
ans++;
}
if(ans)
printf("%d\n",ans);
else
printf("No Special Prime!\n");
}
return 0;
}