C++ :

#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;

const int N = 100007; 
int X1, Y1, X2, Y2;
struct Target {int d1, d2;} t1[N], t2[N];

inline int Dist(int a, int b) {return a * a + b * b;}
bool cmp1(const Target& a, const Target& b) {return a.d1 < b.d1;}
bool cmp2(const Target& a, const Target& b) {return a.d2 < b.d2;}

int main()
{
	int n, i, j, x, y, Res = 0x7fffffff;
	
	cin >> X1 >> Y1 >> X2 >> Y2 >> n;
	for (i = 0; i < n; ++i)
	{
		scanf("%d%d", &x, &y);
		t1[i].d1 = t2[i].d1 = Dist(x - X1, y - Y1);
		t1[i].d2 = t2[i].d2 = Dist(x - X2, y - Y2);
	}
	
	sort(t1, t1 + n, cmp1); sort(t2, t2 + n, cmp2);
	j = n - 1;
	for (i = 0; i < n; ++i)
	{
		while (t2[j].d1 <= t1[i].d1 && j >= 0) --j;
		if (j == -1) Res = min(Res, t1[i].d1);
		else Res = min(Res, t1[i].d1 + t2[j].d2);
	}
	
	cout << Res << endl;
	
	return 0;
}

Pascal :

var x,y,x1,y1,x2,y2,i,n,min,j:longint;
    a,b:array[1..100500]of longint;
    procedure sort(l,r: longint);
      var
         i,j,x,y: longint;
      begin
         i:=l;
         j:=r;
         x:=a[(l+r) div 2];
         repeat
           while a[i]<x do
            inc(i);
           while x<a[j] do
            dec(j);
           if not(i>j) then
             begin
                y:=a[i];
                a[i]:=a[j];
                a[j]:=y;
                y:=b[i];
                b[i]:=b[j];
                b[j]:=y;
                inc(i);
                j:=j-1;
             end;
         until i>j;
         if l<j then
           sort(l,j);
         if i<r then
           sort(i,r);
      end;
begin
  read(x,y,x1,y1);
  read(n);
  for i:=1 to n do
    begin
      read(x2,y2);
      a[i]:=sqr((x2-x))+sqr((y2-y));
      b[i]:=sqr((x2-x1))+sqr((y2-y1));
    end;
  sort(1,n);
  min:=a[n];i:=n;j:=b[n];
  while i>=1 do
    begin
      if b[i]>j then j:=b[i];
      dec(i);
      while (b[i]<=j) and (i>0) do dec(i);
      if a[i]+j<min then min:=a[i]+j;
    end;
  writeln(min);
end.