var n,i,j,k,p,u:int64;
    f:text;
begin
   assign(f,'fact.in');
   reset(f);
   read(f,n);
   close(f);
   assign(f,'fact.out');
   rewrite(f);
   if n=0 then writeln(f,1)
   else
   j:=5*625;
   u:=1+5+25+125+625;
   begin
   repeat
   i:=i+j;
   if(p+u>=n)and(u>1)then begin i:=i-j;
                       j:=j div 5;
                       u:=u-j;
                 end
            else p:=p+u;
    until p=n;
   writeln(f,i);
   end;
   close(f);
end.