#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;
}