#include<bits/stdc++.h>
const int maxn=300;
inline const void read(int &a)
{
	a=0;
	char c=getchar();
	while(c<'0'||c>'9')c=getchar();
	while(c>='0'&&c<='9')
	{
		a=(a<<1)+(a<<3)+c-'0';
		c=getchar();
	}
}
inline const void write(int a)
{
	if(a>=10)write(a/10);
	putchar(a%10+'0');
}
int d=0,n,dis[maxn],step,point[maxn],to[maxn],next[maxn],big=-1;
bool been[maxn];
inline const void add(int a,int b)
{
	next[++d]=point[a];
	to[d]=b;
	point[a]=d;
}
const void dfs(int p)
{
	big=std::max(big,dis[p]);
	been[p]=true;
	int side=point[p];
	while(side>=0)
	{
		if(!been[to[side]]){dis[to[side]]=dis[p]+1;dfs(to[side]);}
		side=next[side];
	}
}
int main()
{
	memset(been,false,sizeof(been));
	memset(dis,0,sizeof(dis));
	memset(point,-1,sizeof(point));
	read(n);read(step);
	int x,y;
	for(int i=1;i<=n-1;i++)
	{read(x);read(y);add(x,y);add(y,x);}
	dis[0]=1;
	dfs(0);
	if(step<=big)write(step);
	else
	{
		int rest=(step-big)/2,ans=rest+big;
		write(ans);
	}
	return 0;
}