This is my first solution. I don't know if I am doing everything all right. I use the Free Pacal Compiler.

Does the output of my solution have to be real, rounded to an integer, or just integer?

This is my solution

program Project2;
var x,y:array[1..100000] of longint;
    r:array[1..100000] of longint;
    d:longint;
    n,i,j:longint;
begin
      readln(n);
      for i:=1 to n do readln(x[i],y[i]);
      for i:=1 to n do r[i]:=0;
      for i:=1 to n do for j:=1 to n do if i<>j then r[i]:=r[i]+(abs(x[j]-x[i])+abs(y[j]-y[i]));
      d:=0;
      for i:=1 to n do begin
                            r[i]:=r[i] div (n-1);
                            d:=d+r[i]
                       end;
      d:=d div n;
      writeln(d)
end.