#include <stdio.h>
#define MAXSIZE 100000000/2/8+1

int getTheNumber(int n) {

int i, j, nr = 1;
char p[MAXSIZE]; //def as 100000000/2/8+1

memset(p, 1, MAXSIZE);

for(i = 1; ((i * i) << 1) + (i << 1) <= n; i += 1){
    if((p[i >> 3] & (1 << (i & 7))) == 0){
        for(j = ((i * i) << 1) + (i << 1); (j << 1) + 1 <= n; j += (i << 1) + 1){
            p[j >> 3] |= (1 << (j & 7));
        }
    }
}
for(i = 1; 2 * i + 1 <= n; ++i){
    if((p[i >> 3] & (1 << (i & 7))) == 0){
        nr++;
    }
}
return nr;
}

int main(){

FILE *file1, *file2;

file1 = fopen("ciur.in", "r");
file2 = fopen("ciur.out", "w");

fscanf(file1, "%d", &N);

fprintf(file2, "%d", getTheNumber(N));

return 0;
}