#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;  
}