C :

#include <stdio.h>
#include <stdlib.h>
int main() {
    int i,a=0;
    float f;
    for(i=0; i<16; i++) {
        int j = 1000;
        int y = 2000;
        if(i&1)  j += y/4, y -= y/4;
        else     y += j/4, j -= j/4;
        if(i&2)  j += y/4, y -= y/4;
        else     y += j/4, j -= j/4;
        if(i&4)  j += y/4, y -= y/4;
        else     y += j/4, j -= j/4;
        if(i&8)  j += y/4, y -= y/4;
        else     y += j/4, j -= j/4;
        if(abs(y-j)<1000)
            ++a; }  
    f = (float)a/16;
    printf("%.3f",f);
    return 0; }

C++ :

#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
#define N 4
int a[N];
int cnt;
void f(int idx)
{
	if(idx==N)
	{
		int A=1000,B=2000;
		for(int i=0;i<N;i++)
		{
			if(a[i])
			{
				A=A+B/4;
			    B=3*B/4;
			}
			else
			{
				B=B+A/4;
			    A=3*A/4;
			}
		}
		if(abs(A-B)<1000) cnt++;
		return;
	}
	a[idx]=0;
	f(idx+1);
	a[idx]=1;
	f(idx+1);
} 
int main()
{
	f(0);
	cout<<fixed<<setprecision(3)<<cnt*1.0/(1<<N);
	return 0;
}

Pascal :

begin
  write('0.625');
end.

Java :

public class Main {
	public static void main(String[] args) {
		System.out.println(0.625);
	}
}