func Push(h Interface, x T) {
	h.Push(x)
	up(h, h.Len()-1)
}
Push pushes the element x onto the heap. The complexity is
O(log(n)) where n = h.Len().
package fnpq
import (
	"sort"
)
type T = *Item
type Interface interface {
	sort.Interface
	Push(x T)  
	Pop() T    
}
func Init(h Interface) {
	n := h.Len()
	for i := n/2 - 1; i >= 0; i-- {
		down(h, i, n)
	}
}