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#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<stack>
#include<cmath>
#include<set>
#include<bitset>
#include<assert.h>
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,l,r) for(int i=l;i>=r;i--)
#define link(x) for(edge *j=h[x];j;j=j->next)
#define mem(a) memset(a,0,sizeof(a))
#define ll long long
#define succ(x) (1<<x)
#define lowbit(x) (x&(-x))
#define sqr(x) ((x)*(x))
#define mid (x+y>>1)
#define NM 250005
#define nm 500005
#define pi 3.1415926535897931
using namespace std;
const ll inf=1e18;
const double eps=1e-8;
ll read(){
ll x=0,f=1;char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
return f*x;
}
struct edge{int t,v;edge*next;}e[nm],*h[NM],*o=e;
void add(int x,int y,int v){o->t=y;o->v=v;o->next=h[x];h[x]=o++;}
int n,m,_x,_y,_t;
ll t;
ll ans;
double d[NM][2];
int g[NM][2];
void dfs(int x,int f){
d[x][0]=d[x][1]=0;g[x][0]=g[x][1]=0;
link(x)if(j->t!=f){
dfs(j->t,x);
d[x][1]+=d[j->t][1],g[x][1]+=g[j->t][1];
if(d[x][1]<d[x][0]+d[j->t][0]+j->v-t)
d[x][1]=d[x][0]+d[j->t][0]+j->v-t,g[x][1]=g[x][0]+g[j->t][0]+1;
else if(d[x][1]==d[x][0]+d[j->t][0]+j->v-t)g[x][1]=max(g[x][1],g[x][0]+g[j->t][0]+1);
d[x][0]+=d[j->t][1],g[x][0]+=g[j->t][1];
if(d[x][0]>d[x][1])d[x][1]=d[x][0],g[x][1]=g[x][0];
else if(d[x][0]==d[x][1])g[x][1]=max(g[x][0],g[x][1]);
}
}
bool check(){
dfs(1,0);
if(d[1][0]>d[1][1])return g[1][0]>=m;else if(d[1][0]<d[1][1])return g[1][1]>=m;
else return max(g[1][0],g[1][1])>=m;
}
int main(){
n=read();m=read();
inc(i,2,n){
_x=read();_y=read();_t=read();
add(_x,_y,_t);add(_y,_x,_t);
}
for(ll x=-n*1e6,y=n*1e6;x<=y;){
t=x+y>>1;
if(check()){
if(d[1][0]>d[1][1])ans=d[1][0]+m*t;
else ans=d[1][1]+m*t;
x=t+1;
}else y=t-1;
}
if(ans==0)return 0*printf("Impossible\n");
return 0*printf("%lld\n",ans);
}
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