void maxheap(int i)
{
int left=i*2,right=i*2+1;
if(a[left]>a[i]&&left<len) big=left;
else big=i;
if(a[right]>a[i]&&right<len) big=right;
swap(big,i);
maxheap(big);
}
int max_extract()
{
if(len<1) {cout<<"error"<<endl;
return;
}
int max=a[1];
a[1]=a[len];
maxheap(1);
len--;
return max;
}
void increase_heap(int key,int i)
{
if(key<a[i])
{
cout<<"error"<<endl;
return;
}
a[i]=key;
while(i>1&&a[i/2]<a[i])
{
swap(a[i],a[i/2]);
i=i/2;
}
}
void insert_heap(int key)
{
a[++len]=INF;
increase_heap(key,len);
}