#include<stdio.h>
#include<math.h>
FILE *f=fopen("cifra.in","r");
FILE *g=fopen("cifra.out","w");
int i,n,r,s,p,k;
int main()
{
p=1;is=1;
fscanf(f,"%d",&n);
s=1;
for(i=2;i<=n;i++) { while(p<=i) { is=is*i;
                                  p++;
                                 }
                    s=s+is;
                    is=1;
                    p=1;
                   }
r=s%10;
fprintf(g,"%d",r);
fclose(f);
fclose(g);
return 0;
}