#include <cstdio>
#define N 999999
unsigned char p[((N+1)/2+7)/8];
int main() {
    int i,j,s,n=3;
    for(i=0;n*n<=N;i++,n+=2)
        if(!(p[i/8]&(1<<(i%8))))
            for(j=i+n;j<((N+1)/2);j+=n)p[j/8]|=(1<<(j%8));
    while(scanf("%d",&n)!=EOF) {
        if(n<2){printf("0\n");continue;}
        if(n==2){printf("1\n");continue;}
        for(i=3,j=0,s=1;i<=n;i+=2,j++)
            s+=!(p[j/8]&(1<<(j%8)));
        printf("%d\n",s);
    }
}