public static String kangaroo(int x1, int v1, int x2, int v2) {
        if ((x2 > x1 && v2 >= v1) || (x1 > x2 && v1 >= v2)) {
            return "NO";
        } else {
            int diff = Integer.MAX_VALUE, p1 = x1 + v1, p2 = x2 + v2;
            while (true) {
                if (p1 == p2) {
                    return "YES";
                } 
                
                if (Math.abs(p1 - p2) > diff) {
                    return "NO";
                }
                
                diff = Math.abs(p1 - p2);
                p1 += v1;
                p2 += v2;
            }
        }
    }