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| #include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
long long read()
{
long long x=0,f=1; char c=getchar();
while(!isdigit(c)){if(c=='-') f=-1;c=getchar();}
while(isdigit(c)){x=x*10+c-'0';c=getchar();}
return x*f;
}
const int M=100000+100;
const int N=50000+100;
const int T=N+M;
struct road
{
int s,t,a,b;
}e[M];
int n,m;
bool cmp(road x,road y)
{
return x.a<y.a;
}
struct LCT
{
int son[T][2],fa[T],lazy[T],MAX[T],num[T],mstack[T],top;
inline void Update(int x)
{
MAX[x]=0;
if(num[MAX[son[x][0]]]>=num[x] and num[MAX[son[x][0]]]>=num[MAX[son[x][1]]])
MAX[x]=MAX[son[x][0]];
if(num[MAX[son[x][1]]]>=num[x] and num[MAX[son[x][1]]]>=num[MAX[son[x][0]]])
MAX[x]=MAX[son[x][1]];
if(num[x]>=num[MAX[son[x][0]]] and num[x]>=num[MAX[son[x][1]]])
MAX[x]=x;
}
inline void Mirror(int x)
{
lazy[x]=!lazy[x],swap(son[x][0],son[x][1]);
}
inline void PushDown(int x)
{
if(lazy[x]==0) return;
lazy[x]=0;
Mirror(son[x][0]),Mirror(son[x][1]);
}
inline bool IsRoot(int x)
{
return x!=son[fa[x]][0] and x!=son[fa[x]][1];
}
inline void Rotate(int x,int type)
{
int y=fa[x],z=fa[y];
if(IsRoot(y)==false) son[z][y==son[z][1]]=x;
fa[x]=z;
son[y][!type]=son[x][type],fa[son[x][type]]=y;
son[x][type]=y,fa[y]=x;
Update(y),Update(x);
}
inline void Splay(int x)
{
mstack[top=1]=x;
for(int i=x;i!=0;i=fa[i])
mstack[++top]=fa[i];
for(int i=top;i>=1;i--)
PushDown(mstack[i]);
while(IsRoot(x)==false)
{
if(x==son[fa[x]][fa[x]==son[fa[fa[x]]][1]] and IsRoot(fa[x])==false)
Rotate(fa[x],x==son[fa[x]][0]),
Rotate(x,x==son[fa[x]][0]);
else
Rotate(x,x==son[fa[x]][0]);
}
}
void Access(int x)
{
for(int t=0;x!=0;t=x,x=fa[x])
Splay(x),son[x][1]=t,fa[t]=x,Update(x);
}
inline void MakeRoot(int x)
{
Access(x),Splay(x);
Mirror(x);
}
inline int FindRoot(int x)
{
Access(x),Splay(x);
while(son[x][0]!=0)
PushDown(x),x=son[x][0];
Splay(x);
return x;
}
inline void Link(int x,int y)
{
if(FindRoot(x)==FindRoot(y)) return;
MakeRoot(x);
fa[x]=y;
}
inline void Split(int x,int y)
{
MakeRoot(x);
Access(y),Splay(y);
}
inline void Cut(int x,int y)
{
Split(x,y);
if(x==son[y][0] and fa[x]==y)
{
son[y][0]=fa[x]=0;
Update(y);
}
}
inline int Query(int x,int y)
{
MakeRoot(x);
Access(y),Splay(y);
return MAX[y];
}
inline void AddLine(int x)
{
if(e[x].s==e[x].t) return;
num[n+x]=e[x].b,MAX[n+x]=n+x;
if(FindRoot(e[x].s)!=FindRoot(e[x].t))
{
Link(n+x,e[x].s),Link(n+x,e[x].t);
return ;
}
int t=Query(e[x].s,e[x].t);
if(num[n+x]<num[t])
{
Cut(e[t-n].s,t);
Cut(e[t-n].t,t);
Link(e[x].s,n+x);
Link(e[x].t,n+x);
}
}
inline int Query2()
{
if(FindRoot(n)!=FindRoot(1)) return 0x3f3f3f3f;
return num[Query(1,n)];
}
}lct;
int main()
{
n=read(),m=read();
for(int i=1;i<=m;i++)
e[i].s=read(),e[i].t=read(),e[i].a=read(),e[i].b=read();
sort(e+1,e+1+m,cmp);
int ans=0x3f3f3f3f;
for(int i=1;i<=m;i++)
{
lct.AddLine(i);
ans=min(ans,e[i].a+lct.Query2());
}
if(ans==0x3f3f3f3f)
printf("-1");
else
printf("%d",ans);
return 0;
}
|
