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#include
#include
#include
using namespace std;
int isPrim[1000010],primeList[1000010],primeCount=0;
int main()
{
memset(isPrim,-1,sizeof(isPrim));
int N;
while(cin>>N)
{
for(int i=2;i<=N;i++)
{
if(isPrim[i]==-1){
primeCount++;
primeList[primeCount]=i;
}
for(int j=1;j<=primeCount;j++)
{
if(i*primeList[j]>N)break;//该树不在判断的范围
isPrim[i*primeList[j]]=0;
if(i%primeList[j]==0)break;
}
}
printf("%d
",primeCount);
}
}