#include<stdio.h>
int main()
{unsigned long w,z,i,n,k[100];
freopen("fact.in","r",stdin);
freopen("fact.out","w",stdout);
scanf("%lu",&n);
if(n==0)
	printf("%lu","1");
k[1]=5;
w=5;
z=0;
for(i=2;i<=100000000;i++)
	{z++;
	if(i==w+z)
	  {w=w+z;
	  k[i]=-1;
	  }
	else
		{z--;
		k[i]=k[i]+5;
		}
	}
printf("%lu",k[n]);
return 0;
}