Help for Algorithm

[ahtoh4o0o]

Hello! I need help to find the longest sublist from the same two lists. I came to the following algorithm, but does not work properly. If anyone has an idea can help.

//start1 and start2->basic lists
//start3 ->new list

void build(elem* start1, elem* start2)
{
	elem *L1, *L2, *p1, *p2;
	elem *Pomoshten=NULL;
	int n(0), br(0);
	
	for(L1=start1; L1; L1=L1->next)
	{
		p1=L1;
		for(L2=start2; L2; L2=L2->next)
		{
			br=0;
			p2=L2;
			while(p1 && p2 && p1->key==p2->key)
			{
				br++;
				Pomoshten=add(Pomoshten, p1->key);
				p1=p1->next;
				p2=p2->next;
			}
			if(br>n)
			{
				start3=NULL;//delete
				start3=Pomoshten;
				Pomoshten=NULL;//delete
				n=br;
				br=0;
			}
			br=0;
		}
	
	}
}