#include <stdio.h>

int i,j,s,N,x,T;

int main () {
    
       FILE *fin = fopen("cifra.in","r");
       FILE *fout = fopen ("cifra.out","w");
       
       fscanf(fin,"%d",&T);
       
       for (i=1;i<=T;i++){
           fscanf(fin,"%d",&N);
           }
           
       s=0;
       for (i=1;i<=N;i++){
           x=1;
           for (j=1;j<=i;j++){
               x=x*i;
               }
           s=(s+(x%10))%10;
           }  
                
       fprintf(fout,"%d",s);                    
                             
    
       fclose(fin);
	   fclose(fout);
    
    
    
    
    
return 0;
}