#include<stdio.h>
#include<string.h>
int n,i,j,k;
long long nr;
char prim[1000001];
int main()
{freopen("fractii.in","r",stdin);
 freopen("fractii.out","w",stdout);
 scanf("%d",&n);
 nr=n;
 for(i=2;i<=n;i++)
 {memset(prim,1,sizeof(prim));
  for(j=2;j<=i;j++)
   if(prim[j]&&i%j==0)
    for(k=j;k<=n;k=k+j)
     prim[k]=0;
  for(j=1;j<=n;j++)
   nr=nr+prim[j];}
 printf("%lld",nr);
 fclose(stdout);
 return 0;}