#include <cstdio>  
  
const int NMAX = 1 << 17;  
  
unsigned char V[NMAX];  
  
int main(void) {  
    freopen("ciur.in", "rt", stdin);  
    freopen("ciur.out", "wt", stdout);  
    int N, i, j, i2, nrprime = 0;  
  
    scanf(" %d", &N);  
  
    for (i = 3; i <= N; i += 2) {  
        if (V[i >> 4] & (1 << ((i >> 1) & 7))) continue;  
        ++nrprime;  
  
        for (j = i + (i2 = i + i); j <= N; j += i2)  
            V[j >> 4] |= 1 << ((j >> 1) & 7);  
    }  
  
    printf("%d\n", nrprime + 1);  
  
    return 0;  
}