stablegradients/pie-gem5-pairs huggingface dataset:
// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;



void Sieve(int n)

{

	bool prime[n+1];

	int c=0;

	memset(prime, true, sizeof(prime));

	int x=sqrt(n*1.0)+2;



	for (int p=2; p<=x; p++)

	{

		if (prime[p] == true)

		{

			for (int i=p*p; i<=n; i+=p)

				{

				    prime[i] = false;

				}



		}

	}

	for (int p=2; p<=n; p++)

	if (prime[p])

		c++;

		cout<<c<<endl;

}



int main()

{

	int n;

	while(cin>>n){

        Sieve(n);

	}



	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.248576768394442x):
#include<cstdio>

using namespace std;

#define MAX 1000000

int prime[MAX];

bool is_prime[MAX];

int sieve(int n){   //埃氏?

   int p=0;

   for(int i=0;i<=n;i++)

    is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

   for(int i=2;i<=n;i++){

    if(is_prime[i]){

        prime[p++]=i;    //??素数的个数和素数的?

        for(int j=2*i;j<=n;j+=i)

            is_prime[j]=false;

    }

   }

   return p;

}

int main()

{

  int num;

  while(scanf("%d",&num)!=EOF){

   printf("%d\n",sieve(num));

  }

  return 0;

}
// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;



void SieveOfEratosthenes(int n)

{

    int c = 0;

    bool prime[n+1];

    memset(prime, true, sizeof(prime));



    for (int p=2; p*p<=n; p++)

    {

        if (prime[p] == true)

        {

            for (int i=p*2; i<=n; i += p)

                prime[i] = false;

        }

    }



    for (int p=2; p<=n; p++)

       if (prime[p]){

            c++;

       }



       cout<<c<<endl;



}



// Driver Program to test above function

int main()

{

    int n;

    while(cin>>n)

    {

        SieveOfEratosthenes(n);

    }



    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.207991308759862x):
#include<cstdio>

using namespace std;

#define MAX 1000000

int prime[MAX];

bool is_prime[MAX];

int sieve(int n){   //埃氏?

   int p=0;

   for(int i=0;i<=n;i++)

    is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

   for(int i=2;i<=n;i++){

    if(is_prime[i]){

        prime[p++]=i;    //??素数的个数和素数的?

        for(int j=2*i;j<=n;j+=i)

            is_prime[j]=false;

    }

   }

   return p;

}

int main()

{

  int num;

  while(scanf("%d",&num)!=EOF){

   printf("%d\n",sieve(num));

  }

  return 0;

}
// Slower C++ solution:
#include<cstdio>

#include<string.h>

using namespace std;

int pNum;

bool IsPrime[1000010];

int Prime[1000010];

int GetPrime(int n){

    memset(IsPrime,true,sizeof(IsPrime));

    IsPrime[0]=IsPrime[1]=false;

    pNum=0;

    for(int i=2;i<=n;i++){

        if(IsPrime[i])Prime[++pNum]=i;

        for(int j=1;j<=pNum&&Prime[j]*i<=n;j++){

            IsPrime[Prime[j]*i]=false;

            if(i%Prime[j]==0)break;

        }

    }

    return pNum;

}

int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",GetPrime(n));

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 7.4376233660683395x):
#include<cstdio>

using namespace std;

#define MAX 1000000

int prime[MAX];

bool is_prime[MAX];

int sieve(int n){   //埃氏?

   int p=0;

   for(int i=0;i<=n;i++)

    is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

   for(int i=2;i<=n;i++){

    if(is_prime[i]){

        prime[p++]=i;    //??素数的个数和素数的?

        for(int j=2*i;j<=n;j+=i)

            is_prime[j]=false;

    }

   }

   return p;

}

int main()

{

  int num;

  while(scanf("%d",&num)!=EOF){

   printf("%d\n",sieve(num));

  }

  return 0;

}
// Slower C++ solution:
#include<stdio.h>

#include<math.h>

bool flag[1000000];

int main(void)

{

	long long i,j,p,n,count;

	p = (long long)sqrt(1000000.0);

	for(i = 3; i <= p; i = i + 2)

	{

		if(flag[i] == false)

		{

			for(j = i * i; j <= 1000000; j = j + 2 * i)

			{

				flag[j] = true;

				

			}

		}

	}

		

	while((scanf("%lld",&n)) != EOF)

	{

		

		if(n == 1 || n == 0)

			count = 0;

		else

		{

			count = 1;

			for(i = 3; i <= n; i = i + 2)

			{

				if(flag[i] == false)

					count++;

			}

		}

		printf("%lld\n",count);

	}

	



		

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 3.511351766152507x):
#include<bits/stdc++.h>

using namespace std;

int main()

{

    int n;

    while(~scanf("%d",&n))

    {

        int prime[n+1];

        for(int i=0;i<=n;i++)

            prime[i]=1;

            prime[0]=0;

            prime[1]=0;

        for(int i=2;i*i<=n;i++)

             if(prime[i]==1)

        {

            for(int j=2;j*i<=n;j++)

            prime[i*j]=0;

        }

        int c=0;

        for(int i=0;i<=n;i++)

        {

            if(prime[i]==1)

                c++;

        }

        printf("%d\n",c);

    }



}
// Slower C++ solution:
#include <iostream>

#include <cstdio>

#include <string>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <vector>

#include <queue>

using namespace std;

#define MAX 1000000

#define LMT 1000

unsigned flag[MAX>>6];

int primes[6000000];//5761455

#define ifc(n) (flag[n>>6]&(1<<((n>>1)&31)))

#define isc(n) (flag[n>>6]|=(1<<((n>>1)&31)))



int sieve()

{

    unsigned i, j, k;

    for(i=3; i<LMT; i+=2)

        if(!ifc(i))

            for(j=i*i, k=i<<1; j<MAX; j+=k)

                isc(j);

    return 0;

}



int main()

{

    sieve();

    unsigned int i,L;

    int k=1, count;

    primes[0]=2;

    while(scanf("%d", &L)==1)

    {

        count=1;

        for( i=3; i<=L; i+=2)

        {

            if(ifc(i)==0)

                count++;

        }

        if(L>1)

            printf("%d\n", count);

        else printf("0\n");

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 2.4002535600378234x):
#include<bits/stdc++.h>

using namespace std;

int main()

{

    int n;

    while(~scanf("%d",&n))

    {

        int prime[n+1];

        for(int i=0;i<=n;i++)

            prime[i]=1;

            prime[0]=0;

            prime[1]=0;

        for(int i=2;i*i<=n;i++)

             if(prime[i]==1)

        {

            for(int j=2;j*i<=n;j++)

            prime[i*j]=0;

        }

        int c=0;

        for(int i=0;i<=n;i++)

        {

            if(prime[i]==1)

                c++;

        }

        printf("%d\n",c);

    }



}
// Slower C++ solution:
#include<iostream>

#include<cstring>

#include<cmath>

using namespace std;



bool prime[1000000];



int main()

{

    int i,j,k,l,m,n;

    int count;

    while(cin>>n)

    {

        memset(prime,0,sizeof(prime));

        prime[1]=1;

        prime[2]=0;



        count=0;



        for(j=2;j*j<=n;j++)

        {

            if(prime[j]==0)

            {

                for(k=2;k*j<=n;k++)

                {

                   prime[j*k]=1;

                }

            }

        }

        for(i=1;i<=n;i++)

        {

            if(prime[i]==0)

            count++;

        }

        cout << count << endl;

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 2.2869467232331764x):
#include<bits/stdc++.h>

using namespace std;

int main()

{

    int n;

    while(~scanf("%d",&n))

    {

        int prime[n+1];

        for(int i=0;i<=n;i++)

            prime[i]=1;

            prime[0]=0;

            prime[1]=0;

        for(int i=2;i*i<=n;i++)

             if(prime[i]==1)

        {

            for(int j=2;j*i<=n;j++)

            prime[i*j]=0;

        }

        int c=0;

        for(int i=0;i<=n;i++)

        {

            if(prime[i]==1)

                c++;

        }

        printf("%d\n",c);

    }



}
// Slower C++ solution:
#include<iostream>

#include<cstring>

#include<math.h>

using namespace std;

const int MAX = 1000000;

int prime(int n)

{

	int ans = 0;

	bool prime[MAX];

	memset(prime, 0, sizeof(prime));

	for (int i = 2; i < n;i++)  

	{ 

		for (int j = 2; j <= n / i; j++)

		{

			if (i*j <= n)

				prime[i*j] = 1;

		}

	}

	for (int i = 2; i <= n; i++)

	{

		if (!prime[i])

			ans++;

	}

	return ans;

}

int main()

{

	int n, m = 0;

	while (cin >> n&&m<30)

	{

		cout << prime(n) << endl;

		m++;

	}

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 2.301920364073553x):
#include<bits/stdc++.h>

using namespace std;

int main()

{

    int n;

    while(~scanf("%d",&n))

    {

        int prime[n+1];

        for(int i=0;i<=n;i++)

            prime[i]=1;

            prime[0]=0;

            prime[1]=0;

        for(int i=2;i*i<=n;i++)

             if(prime[i]==1)

        {

            for(int j=2;j*i<=n;j++)

            prime[i*j]=0;

        }

        int c=0;

        for(int i=0;i<=n;i++)

        {

            if(prime[i]==1)

                c++;

        }

        printf("%d\n",c);

    }



}
// Slower C++ solution:
#include<cstdio>

#include<string.h>

using namespace std;

int pNum;

bool IsPrime[1000010];

int Prime[1000010];

int GetPrime(int n){

    memset(IsPrime,true,sizeof(IsPrime));

    IsPrime[0]=IsPrime[1]=false;

    pNum=0;

    for(int i=2;i<=n;i++){

        if(IsPrime[i])Prime[++pNum]=i;

        for(int j=1;j<=pNum&&Prime[j]*i<=n;j++){

            IsPrime[Prime[j]*i]=false;

            if(i%Prime[j]==0)break;

        }

    }

    return pNum;

}

int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",GetPrime(n));

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 1.4467966181607401x):
#include<bits/stdc++.h>

using namespace std;

int main()

{

    int n;

    while(~scanf("%d",&n))

    {

        int prime[n+1];

        for(int i=0;i<=n;i++)

            prime[i]=1;

            prime[0]=0;

            prime[1]=0;

        for(int i=2;i*i<=n;i++)

             if(prime[i]==1)

        {

            for(int j=2;j*i<=n;j++)

            prime[i*j]=0;

        }

        int c=0;

        for(int i=0;i<=n;i++)

        {

            if(prime[i]==1)

                c++;

        }

        printf("%d\n",c);

    }



}
// Slower C++ solution:
#include<stdio.h>

#include<math.h>

bool flag[1000000];

int main(void)

{

	long long i,j,p,n,count;

	p = (long long)sqrt(1000000.0);

	for(i = 3; i <= p; i = i + 2)

	{

		if(flag[i] == false)

		{

			for(j = i * i; j <= 1000000; j = j + 2 * i)

			{

				flag[j] = true;

				

			}

		}

	}

		

	while((scanf("%lld",&n)) != EOF)

	{

		

		if(n == 1 || n == 0)

			count = 0;

		else

		{

			count = 1;

			for(i = 3; i <= n; i = i + 2)

			{

				if(flag[i] == false)

					count++;

			}

		}

		printf("%lld\n",count);

	}

	



		

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 18.0504840750859x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include <iostream>

#include <cstdio>

#include <string>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <vector>

#include <queue>

using namespace std;

#define MAX 1000000

#define LMT 1000

unsigned flag[MAX>>6];

int primes[6000000];//5761455

#define ifc(n) (flag[n>>6]&(1<<((n>>1)&31)))

#define isc(n) (flag[n>>6]|=(1<<((n>>1)&31)))



int sieve()

{

    unsigned i, j, k;

    for(i=3; i<LMT; i+=2)

        if(!ifc(i))

            for(j=i*i, k=i<<1; j<MAX; j+=k)

                isc(j);

    return 0;

}



int main()

{

    sieve();

    unsigned int i,L;

    int k=1, count;

    primes[0]=2;

    while(scanf("%d", &L)==1)

    {

        count=1;

        for( i=3; i<=L; i+=2)

        {

            if(ifc(i)==0)

                count++;

        }

        if(L>1)

            printf("%d\n", count);

        else printf("0\n");

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 12.338763401396344x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include <iostream>

#include <cstring>

#include <cmath>



using namespace std;





int main()

{

    unsigned int n;

    while( cin >> n )

    {

        bool *prime = new bool[n+2];

        unsigned int k, allprime = 0;



        memset( prime, false, n+2 );

        prime[2] = true;

        for( int i = 3; i <= n; i++ )

        {

            if( i % 2 == 0 )

            {

                prime[i] = false;

            }

            else

            {

                prime[i] = true;

            }

        }

        k = sqrt( n );

        for( int i = 3; i <= k; i++ )

        {

            for( int j = i + i; j <= n; j += i )

            {

                prime[j] = false;

            }

        }

        for( int i = 2; i <= n; i++ )

        {

            if( prime[i] )

            {

                allprime++;

            }

        }

        cout << allprime << '\n';

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.207586738747994x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include<iostream>

#include<cmath>

using namespace std;

bool prime[1000000] = {false};

int main(){

    int n;

    while(cin >> n){

       

        prime[1] = true;

        prime[2] = false;

        int count = 0;

        

      

        for(int j = 2; j * j <= n ; j++){

            if(!prime[j]){

                for (int k = 2; k*j <= n;k++){

                   prime[j*k] = true;

                }

            }

        }

        for(int i = 1;i<=n;i++){

            if(!prime[i]) count = count +1;

        }

        cout << count << endl;

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.207209302951794x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include<iostream>

#include<cstring>

#include<cmath>

using namespace std;



bool prime[1000000];



int main()

{

    int i,j,k,l,m,n;

    int count;

    while(cin>>n)

    {

        memset(prime,0,sizeof(prime));

        prime[1]=1;

        prime[2]=0;



        count=0;



        for(j=2;j*j<=n;j++)

        {

            if(prime[j]==0)

            {

                for(k=2;k*j<=n;k++)

                {

                   prime[j*k]=1;

                }

            }

        }

        for(i=1;i<=n;i++)

        {

            if(prime[i]==0)

            count++;

        }

        cout << count << endl;

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 11.756297334323358x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include<iostream>

#include<cstring>

#include<math.h>

using namespace std;

const int MAX = 1000000;

int prime(int n)

{

	int ans = 0;

	bool prime[MAX];

	memset(prime, 0, sizeof(prime));

	for (int i = 2; i < n;i++)  

	{ 

		for (int j = 2; j <= n / i; j++)

		{

			if (i*j <= n)

				prime[i*j] = 1;

		}

	}

	for (int i = 2; i <= n; i++)

	{

		if (!prime[i])

			ans++;

	}

	return ans;

}

int main()

{

	int n, m = 0;

	while (cin >> n&&m<30)

	{

		cout << prime(n) << endl;

		m++;

	}

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 11.833270956886793x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:


#include<iostream>

#include<cstdio>

#include<cstdlib>

using namespace std;



const int MAX_N = 999999;

int prime[MAX_N];

bool is_prime[MAX_N + 1];



int sieve(int n)

{

	int p = 0;

	for (int i = 0; i <= n; i++)

		is_prime[i] = true;

	is_prime[0] = is_prime[1] = false;



	for (int i = 2; i <= n; i++)

	{

		if (is_prime[i])

		{

			prime[p++] = i;

			for (int j = i * 2; j <= n; j += i)

				is_prime[j] = false;

		}

	}

		return p;

}



int main()

{

	int n;

	while (scanf("%d", &n) != EOF)

	{

		int ans = sieve(n);

		printf("%d\n", ans);

	}

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.1447506882839225x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include<iostream>

#include<cstdlib>

#include<algorithm>

#include<cstdio>

using namespace std;



//C



const int MAX_N = 1000000;

int prime[MAX_N];

bool is_prime[MAX_N + 1];



int sieve(int n){

	int p = 0;

	for (int i = 0; i <= n; i++)is_prime[i] = true;

	is_prime[0] = is_prime[1] = false;

	for (int i = 2; i <= n; i++)

	{

		if (is_prime[i]){

			prime[p++] = i;

			for (int j = 2 * i; j <= n; j += i)is_prime[j] = false;

		}

	}

	return p;

}



int main(){

	int n;

	while (scanf("%d", &n) != EOF)

	{

		int ans = sieve(n);

		printf("%d\n", ans);

	}

}

// Faster C++ solution for the same problem (measured speedup: 5.144837154305632x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include<iostream>

#include<cstdio>

#include<cmath>

#define size 20000000

using namespace std;

int find_prime(int n)

{

    int count =0;

    bool *numberList=new bool[size+1];

    for(unsigned long i=3;i<=sqrt(n);i+=2)

    {

        for(unsigned long j=i;i*j<=n;j+=2)

            numberList[i*j]=true;

    }

    for (unsigned long i=3;i<=n;i+=2)

    {

        if(!numberList[i])

            count++;

    }



    return count;



}

int main ()

{

    int n;

    while((scanf("%d",&n))!=EOF)

    {

        if(n==1||n==0)

            printf("0\n");

        else if(n==2)

            printf("1\n");



        else

        {

        int v=0;

        v=find_prime(n);

        printf("%d\n",v+1);

        }

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.189820642629321x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include<iostream>

using namespace std;

bool Eratosthenes[999999+30];



int main()

{

    int n,pos;

    int c;



    while(cin>>n)

    {

        c=0;

        Eratosthenes[1]=false;



        for(int i=2; i<=n; i++) Eratosthenes[i]=true;

        for(int i=2; i<=n; i++)

        {

            if(Eratosthenes[i]==true)

            {

                pos=2*i;

                while(pos<=n)

                {

                    Eratosthenes[pos]=false;

                    pos=pos+i;

                }

            }

        }

        for(int i=1; i<=n; i++)

        {

            if(Eratosthenes[i]==true)

                c++;

        }

        cout<<c<<endl;



    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.208931043896202x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}
// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e7+1;

int prime[maxn];

bool is_prime[maxn];



int sieve(int n) {

    int p = 0;

    for(int i = 1; i <= n; i ++) is_prime[i] = true;

    is_prime[0] = is_prime[1] = false;

    for(int i = 2; i <= n; i ++) {

        if(is_prime[i]) {

            prime[p++] = i;

            for(int j = i+i; j <= n; j += i) {

                is_prime[j] = false;

            }

        }

    }

    return p;

}



int main() {

    int n;

    while(scanf("%d", &n) != EOF) {

        printf("%d\n", sieve(n));

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.1421076119149065x):
#include<cstdio>

using namespace std;

#define MAX_N 999999+10

int prime[MAX_N];

bool is_prime[MAX_N+1];



int sieve(int n){

    int p=0;

    for(int i=0;i<=n;i++)is_prime[i]=true;

    is_prime[0]=is_prime[1]=false;

    for(int i=2;i<=n;i++){

        if(is_prime[i]){

            prime[p++]=i;

            for(int j=2*i;j<=n;j+=i)is_prime[j]=false;

        }

    }

    return p;

}



int main(){

    int n;

    while(~scanf("%d",&n)){

        printf("%d\n",sieve(n));

    }

}