var a:array[0..14]of real;
i,n:longint;
m,s:real;
input,output:text;
 begin
 assign (input,'input.txt');reset(input);
assign (output,'output.txt');rewrite(output);
read(input,n);
s:=0;
for i:=1 to n do begin read(input,a[i]); s:=s+a[i]end;
write(output,s/3:0:0);
close(input);
  close(output);

end.