import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

// Java Iterator interface reference:

// https://docs.oracle.com/javase/8/docs/api/java/util/Iterator.html

class PeekingIterator implements Iterator<Integer>

{

List<Integer> list = new ArrayList<>();

int _step, _count;

public PeekingIterator( Iterator<Integer> iterator )

{

// initialize any member here.

while ( iterator.hasNext() )

list.add( iterator.next() );

_count = list.size();

_step = 0;

}

// Returns the next element in the iteration without advancing the iterator.

public Integer peek()

{

return list.get( _step );

}

// hasNext() and next() should behave the same as in the Iterator interface.

// Override them if needed.

@Override

public Integer next()

{

int step = _step;

_step++;

return list.get( step );

}

@Override

public boolean hasNext()

{

return _count - _step == 0 ? false : true;

}

}