#include <bits/stdc++.h>
using namespace std;
#define MAXN 100000
// Edmonds minimal branching algorithm
typedef struct EdgeStruct Edge;
vector<Edge> incoming[2*MAXN]; // Stores incoming edges
struct UFVal // Disjoint set union find data structure, used for supernodes
{
	int rep[2*MAXN]; // Stores the highest node we know on the path from this node to its root
	int val[2*MAXN]; // Stores sum of all values on the path from the node to its root, excluding the value of the root 
	int valatroot[2*MAXN]; // Stores the value at a root, or what value it had when it was a root
	int upto;
	UFVal() // Initialises the union find for MAXN elements
	{
		upto = MAXN;
		for (int i = 0; i < 2*MAXN; i++) rep[i] = i;
	}
	int findrep(int a) // Finds the root of the tree that a is in. Updates the value of a as well
	{
		if (rep[a] == a) return a;
		int b = rep[a];
		rep[a] = findrep(b);
		val[a] += val[b] + valatroot[a];
		valatroot[a] = 0;
		return rep[a];
	}
	bool connected(int a, int b) // Are a and b connected?
	{
		return findrep(a) == findrep(b);
	}
	void merge(int a, int b) // Joins the sets containing a and b
	{
		// Set a and b to their roots
		a = findrep(a);
		b = findrep(b);
		assert(a != b);
		rep[a] = b;
	}
	void addval(int a, int val) // Adds val to the set containing a
	{
		a = findrep(a);
		valatroot[a] += val;
	}
	int findval(int a) // Returns the value of node a
	{
		int b = findrep(a);
		return val[a] + valatroot[b];
	}
};
struct UF // Simpler union find data structure that does not need to support adding a value. Used to see if a path exists between two nodes
{
	int rep[MAXN];
	UF()
	{
		for (int i = 0; i < MAXN; i++) rep[i] = i;
	}
	int findrep(int a)
	{
		if (rep[a] == a) return a;
		return rep[a] = findrep(rep[a]);
	}
	bool connected(int a, int b)
	{
		return findrep(a) == findrep(b);
	}
	void merge(int a, int b)
	{
		rep[findrep(a)] = findrep(b);
	}
};
UFVal supernodes; // Stores all the compacted 'supernodes'
UF trees; // Stores all the trees that have been constructed so far
struct EdgeStruct // Stores a directed edge from u to v
{
	int u, v;
	int weight;
	int val() // Returns the corrected weight of this edge, i.e. weight - the value subtracted from all edges going into v
	{
		return weight - supernodes.findval(v);
	}
	bool operator== (const EdgeStruct e) const
	{
		return e.u == u && v == e.v && weight == e.weight;
	}
};
int n, m;
int ans; // Stores the weight of the minimum spanning tree
queue<int> roots; // Stores all the roots to be processed
Edge par[2*MAXN]; // Stores the parent edge of a node, used to find cycles
int main()
{
	// Scan in input
	scanf("%d%d", &n, &m);
	int r;
	scanf("%d", &r);
	for (int i = 0; i < m; i++)
	{
		int a, b;
		int c;
		scanf("%d%d%d", &a, &b, &c);
		Edge e;
		e.u = a;
		e.v = b;
		e.weight = c;
		incoming[b].push_back(e);
	}
	// Push all nodes onto the queue to be processed, except the root
	for (int i = 0; i < n; i++)
	{
		if (i != r) roots.push(i);
	}
	// Run the algorithm
	while (!roots.empty())
	{
		int a = roots.front();
		roots.pop();
		if (a != supernodes.findrep(a)) continue; // Ensure a is the root
		// Find the minimum incoming edge
		Edge e;
		while (true)
		{
			if (incoming[a].empty()) assert(false); // If this is the case, branching is not possible
			e = incoming[a][0];
			for (int i = 1; i < incoming[a].size(); i++)
			{
				if (incoming[a][i].val() < e.val()) e = incoming[a][i];
			}
			// Must remove this edge
			for (int i = 0; i < incoming[a].size(); i++)
			{
				if (incoming[a][i] == e) 
				{
					incoming[a].erase(incoming[a].begin()+i, incoming[a].begin()+i+1);
					break;
				}
			}
			if (!supernodes.connected(e.u, e.v)) break; // We have found the edge!
 		}
 		ans += e.val(); // Add value to the answer
 		par[a] = e; 
 		if (trees.findrep(e.u) != trees.findrep(e.v)) // They are in different trees
 		{
 			trees.merge(e.u, e.v);
 		}
 		else // They are in the same tree, therefore a cycle was formed. Contract into a supernode
 		{
 			Edge mxedge = e; // Maximum edge on the cycle
 			int b = supernodes.findrep(e.u);
 			while (b != a) // Find the cycle, up
 			{
 				if (par[b].val() > mxedge.val()) mxedge = par[b]; // Update maximum edge if needed
 				b = supernodes.findrep(par[b].u);
 			}
 			// Remove mxedge from cost
 			ans -= mxedge.val();
 			
 			int s = supernodes.upto++; // New supernode
 			// Go over the cycle again, merging the incoming edge lists
 			b = supernodes.findrep(e.u);
 			while (supernodes.findrep(b) != s)
 			{
 				// Subtract weight of par[b] - mxedge from the weight of all edges going into b
 				supernodes.addval(b, par[b].val() - mxedge.val());
 				// Merge the incoming edges of b into a
 				for (auto c : incoming[b])
 				{
 					incoming[s].push_back(c);
 				}
 				// Merge b and a
 				supernodes.merge(b, s);
 				b = supernodes.findrep(par[b].u);
 			}
 			roots.push(s);
 		}
	}
	// Print the answer
	printf("%d\n", ans);
}


Measured memory_bytes: 9288