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[AdditionalFile140.zip](file://AdditionalFile140.zip?type=additional_file)

Description

Hint

#include<bits/stdc++.h>
using namespace std;
const int N = 110;
struct edge{int x,y,w;};
vector<edge>E;
int n,m,rt,in[N],pre[N],scc[N],vis[N];
int solve()
{
	int ans=0;
	while(True)
	{
		memset(in, 0x3f, sizeof(in));
		memset(pre, 0, sizeof(pre));
		memset(scc, 0, sizeof(scc));
		memset(vis, 0, sizeof(vis));
	for(auto e:E)if(e.x!=e.y &amp;&amp; e.w&lt;in[e.y])in[e.y]=e.w&#44;pre[e.y]=e.x;
	for(int i=1;i&lt;=n;++i)if(i!=rt&amp;&amp;pre[i]==0) return -1;
	for(int i=1;i&lt;=n;++i)if(i!=rt)ans+=in[i];
	
	int cnt = 0;
	for(int i=1&#44;x;i&lt;=n;++i)if(!scc[i])
	{
		for(x=i; x!=rt &amp;&amp; !scc[x] &amp;&amp; vis[x]!=i; x=pre[x]) vis[x]=i;
		if(x!=rt &amp;&amp; !scc[x])
		{
			for(++cnt;!scc[x];x=pre[x]) scc[x]=cnt;
		}
	}
	if(cnt==0) return ans;
	for(int i=1;i&lt;=n;++i)if(!scc[i]) scc[i]=++cnt;
	
	for(int i=0;i&lt;E.size();i++)
	{
		E[i].w=E[i].w-in[E[i].y];
		E[i].x=scc[E[i].x];E[i].y=scc[E[i].y];
	}
	n=cnt;
	rt=scc[rt];
}

}
int main()
{
scanf("%d%d%d",&n,&m,&rt);
for(int i=1,x,y,w;i<=m;++i)
{
scanf("%d%d%d",&x,&y,&w);if(xy||yrt) continue;
E.push_back(edge{x,y,w});
}
printf("%d",solve());
return 0;
}