#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;
}