#include <fstream>
#include <string>
#include<stdlib>
using namespace std ;
unsigned int putere (unsigned long x)
{
unsigned int c=x%10,r ;
switch(c)
{case 0 :r=0 ;break;
case 1 :r=1 ;break ;
case 2 :
if(x%4==0)
r=6 ;
else
if(x%4==1)
r=2;
else
if(x%4==2)
r=4 ;
else
r=8;break    ;
case 3:
if(x%4==0)
r=1;
else
if(x%4==1)
r=3 ;
else
if(x%4==2)
r=9;
else
r=7;break ;
case 4:
if(x%2==0)
r=6 ;
else
r=4  ;break ;
case 5: r=5 ;break ;
case 6:r=6 ;break   ;
case 7:
if(x%4==0)
r=1 ;
else
if(x%4==1)
r=7 ;
else
if(x%4==2)
r=9 ;
else
r=3;break   ;
case 8:
if(x%4==0)
r=6 ;
else
if(x%4==1)
r=8;
else
if(x%4==2)
r=4 ;
else
r=2;break   ;
case 9 :
if(x%2==0)
r=9;
else
r=1 ;break   ;
}
return r;
}
int main()
{
char n[102];
unsigned int i,s=0;
fstream f("cifra.in",ios::in), g("cifra.out",ios::out) ;
f>>n;
if(strlen(n)>2)
strcpy(n,n+strlen(n)-2)  ;
int x=atoi(n);

for(i=1;i<=x;i++)
{
s=(s+putere(i))%10;
}    g<<s;
f.close() ;
g.close() ;
return 0;
}