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#include <iostream>
int MAXSIZE = 100000000/2/8+1;
using namespace std;
char p[1000];
int n,i,j,nr=1;
int main()
{
cin>>n;
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++;
cout<<nr<<" ";
return 0;
}