/**#include <stdio.h>
int n, m, x;
/// 다이라믹 노동
int max(int p, int q){ return p>=q?p:q;}
int min(int p, int q){ return p<q?p:q;}
int mid (int a, int b,int c)
{
if (a<b)
{
if (b<c)
{
return b;
}else
{
return c;
}
}else
{
if (a<c)
{
return a;
}else
{
return b;
}
}
}
int main()
{
scanf("%d%d%d", &n, &m, &x);
printf("%d\n", mid(n, m, x));
}
*//*
#include <stdio.h>
int i,k;
void rec (int k)
{
if (k>i) return;
printf ("%d\n",k);
rec (k+1);
}
int main ()
{
scanf ("%d",&i);
rec (1);
}
*//*
#include <stdio.h>
int aa,AA;
void beautifully(int a)
{
if (a==AA+1)
{
return;
}if (a%2==1)
{
printf ("%d ",a);
}beautifully (a+1);
}
int main ()
{
scanf("%d %d",&aa,&AA);
beautifully(aa);
}
*/
#include <stdio.h>
int b;
void beautifully (int B)
{
int c;
if (B==b+1)
{
printf("%d",c);
return;
}
c+=B;
beautifully (B++)
}
int main ()
{
scanf ("%d",&b);
beautifully (b);
}