#include <cstdio>

int main() {
int i,n,k,ult,j;
freopen("cifra.in","r",stdin);
freopen("cifra.out","w",stdout);
scanf("%d", &n);
k=0;
for(i=1; i<=n; i++)
{
     ult=1;
      for(j=1; j<=i; j++)
        ult=ult*i % 10;
      k=(k+ult) % 10;
}
printf("%d", k);
return 0;
}