/*
 * fudq.cpp
 *
 *  Created on: 2015-10-24
 *      Author: bjfudq
 */
#include <functional>
#include <algorithm>
#include <iostream>
//#include <fstream>
#include <sstream>
#include <iomanip>
#include <numeric>
#include <cstring>
#include <cassert>
#include <cstdio>
#include <string>
#include <vector>
#include <bitset>
#include <queue>
#include <stack>
#include <cmath>
#include <ctime>
#include <list>
#include <set>
#include <map>
using namespace std;
//#pragma comment(linker,"/STACK:102400000,102400000")


#define MEM(a) (memset((a),0,sizeof(a)))
#define LEN(a) (int)strlen((a))
#define fr(a) for(int i=0;i<(a);i++)
#define sf(a) scanf("%d",&(a))
#define sf64(a) scanf("%I64d",&(a))
#define sff(a) scanf("%lf",&(a))
#define sfs(a) scanf("%s",(a))
#define sf2(a,b) scanf("%d%d",&(a),&(b))
#define sf3(a,b,c) scanf("%d%d%d",&(a),&(b),&(c))
#define sf2s(a,b) scanf("%s%s",(a),(b))
#define sf2f(a,b) scanf("%lf%lf",&(a),&(b))
#define sf3f(a,b,c) scanf("%lf%lf%lf",&(a),&(b),&(c))
#define sf264(a,b) scanf("%I64d%I64d",&(a),&(b))
#define sf364(a,b,c) scanf("%I64d%I64d%I64d",&(a),&(b),&(c))
#define pf(a) printf("%d\n",(a))
#define pfc(a) printf("%c",(a))
#define pf64(a) printf("%I64d\n",(a))
#define pff(a) printf("%lf\n",(a))
#define pfs(a) printf("%s\n",(a))
#define pf2(a,b) printf("%d %d\n",(a),(b))
#define pf2s(a,b) printf("%s%s\n",(a),(b));
#define pf2f(a,b) printf("%lf %lf\n",(a),(b))
#define pf264(a,b) printf("%I64d %I64d\n",(a),(b))
#define pfn printf("\n")
#define pfk printf(" ")
#define LL long long

const int N=1000010;
const int M=1000010;
const int MOD=1000000007;
const int INF=0x3f3f3f3f;
const int dir4[4][2]={{-1,0},{1,0},{0,-1},{0,1}};
const int dir8[8][2]={{-1,0},{-1,1},{0,1},{1,1},{1,0},{1,-1},{0,-1},{-1,-1}};
const double eps=1e-12;
const double PI=acos(-1.0);

inline int sign(double x){return (x>eps)-(x<-eps);}
template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
template<class T> inline T Min(T a,T b){return a<b?a:b;}
template<class T> inline T Max(T a,T b){return a>b?a:b;}
/*************************/

int tot,prime[N+10],f[N+10];

void Getprime()
{
	memset(f,0,sizeof(f));
	tot=0;
	for(int i=2;i<=N;i++)
	{
		if(f[i] == 0)
			prime[tot++]=f[i]=i;
		for(int j=0;j<tot && prime[j]<=f[i] && i*prime[j]<=N;j++)
			f[i*prime[j]]=prime[j];
	}
}



int main(){
    Getprime();
    int n;
    while(sf(n)!=EOF){
    	int p=lower_bound(prime,prime+tot,n)-prime;
    	if(prime[p] != n) p--;
    	pf(p+1);
    }
    return 0;
}