1 type arr=array[0..10000] of longint; 2 var a,b:arr; 3     i,n,m,sum:longint; 4  procedure sort(var a:arr;l,r: longint); 5       var 6          i,j,x,y: longint; 7       begin 8          i:=l; 9          j:=r;10          x:=a[(l+r) div 2];11          repeat12            while a[i]<x do13             inc(i);14            while x<a[j] do15             dec(j);16            if not(i>j) then17              begin18                 y:=a[i];19                 a[i]:=a[j];20                 a[j]:=y;21                 inc(i);22                 j:=j-1;23              end;24          until i>j;25          if l<j then26            sort(a,l,j);27          if i<r then28            sort(a,i,r);29       end;30 begin31     readln(n,m);32     for i:=1 to m do readln(a[i],b[i]);33     sort(a,1,m);34     sort(b,1,m);35     sum:=0;36     for i:=1 to m do sum:=sum+abs(a[i]-b[i]);37     writeln(sum);38 39 end.