#include <bits/stdc++.h>
using namespace std;

using vi = vector<int>; using vvi = vector<vi>; using vvvi = vector<vvi>;
using ll = long long int;
using vll = vector<ll>; using vvll = vector<vll>; using vvvll = vector<vvll>;
using vd = vector<double>; using vvd = vector<vd>; using vvvd = vector<vvd>;
using P = pair<int, int>;
using Pll = pair<ll, ll>;
using cdouble = complex<double>;

const double eps = 1e-7;
#define Loop(i, n) for(int i = 0; i < int(n); i++)
#define Loopll(i, n) for(ll i = 0; i < ll(n); i++)
#define Loop1(i, n) for(int i = 1; i <= int(n); i++)
#define Loopll1(i, n) for(ll i = 1; i <= ll(n); i++)
#define Loopr(i, n) for(int i = int(n) - 1; i >= 0; i--)
#define Looprll(i, n) for(ll i = ll(n) - 1; i >= 0; i--)
#define Loopr1(i, n) for(int i = int(n); i >= 1; i--)
#define Looprll1(i, n) for(ll i = ll(n); i >= 1; i--)
#define Foreach(buf, container) for(auto buf : container)
#define Loopdiag(i, j, h, w, sum) for(int i = ((sum) >= (h) ? (h) - 1 : (sum)), j = (sum) - i; i >= 0 && j < (w); i--, j++)
#define Loopdiagr(i, j, h, w, sum) for(int j = ((sum) >= (w) ? (w) - 1 : (sum)), i = (sum) - j; j >= 0 && i < (h); j--, i++)
#define Loopdiagsym(i, j, h, w, gap) for (int i = ((gap) >= 0 ? (gap) : 0), j = i - (gap); i < (h) && j < (w); i++, j++)
#define Loopdiagsymr(i, j, h, w, gap) for (int i = ((gap) > (h) - (w) - 1 ? (h) - 1 : (w) - 1 + (gap)), j = i - (gap); i >= 0 && j >= 0; i--, j--)
#define Loopitr(itr, container) for(auto itr = container.begin(); itr != container.end(); itr++)
#define printv(vector) Loop(ex_i, vector.size()) { cout << vector[ex_i] << " "; } cout << endl;
#define printmx(matrix) Loop(ex_i, matrix.size()) { Loop(ex_j, matrix[ex_i].size()) { cout << matrix[ex_i][ex_j] << " "; } cout << endl; }
#define quickio() ios::sync_with_stdio(false); cin.tie(0);
#define bitmanip(m,val) static_cast<bitset<(int)m>>(val)
#define Comp(type_t) bool operator<(const type_t &another) const
#define fst first
#define snd second
#define INF INFINITY
bool feq(double x, double y) { return abs(x - y) <= eps; }
bool inrange(ll x, ll t) { return x >= 0 && x < t; }
bool inrange(vll xs, ll t) { Foreach(x, xs) if (!(x >= 0 && x < t)) return false; return true; }
int ceillog2(ll x) { int ret = 0;	x--; while (x > 0) { ret++; x >>= 1; } return ret; }
ll rndf(double x) { return (ll)(x + (x >= 0 ? 0.5 : -0.5)); }
ll floorsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (m * m <= x ? 0 : -1); }
ll ceilsqrt(ll x) { ll m = (ll)sqrt((double)x); return m + (x <= m * m ? 0 : 1); }
ll rnddiv(ll a, ll b) { return (a / b + (a % b * 2 >= b ? 1 : 0)); }
ll ceildiv(ll a, ll b) { return (a / b + (a % b == 0 ? 0 : 1)); }
ll gcd(ll m, ll n) { if (n == 0) return m; else return gcd(n, m % n); }
ll lcm(ll m, ll n) { return m * n / gcd(m, n); }

/*******************************************************/

// solve MCA
class Chuliu_Edmonds {
private:
	struct edge_t {
		int id;
		ll cost;
		stack<int> included_stk;
		bool operator<(const edge_t & another) const {
			return cost > another.cost;
		}
	};
	// edges are directed to the node itself
	struct node {
		int overnode; bool done; bool fin; priority_queue<edge_t> edges; edge_t from;
	};
	vector<node> nodes;
	int n, root;
	stack<int> stk;
	bool no_mca;
	int topnode(int k) {
		int a = k;
		while (nodes[a].overnode != -1) {
			a = nodes[a].overnode;
		}
		if (k != a) nodes[k].overnode = a;
		return a;
	}
	void contract(int s) {
		int a = s;
		priority_queue<edge_t> new_from_edges;
		int cnt = 0;
		do {
			a = topnode(a);
			while (nodes[a].edges.size()) {
				edge_t edge = nodes[a].edges.top();
				nodes[a].edges.pop();
				if (edge.id == nodes[a].from.id) continue;
				edge.cost -= nodes[a].from.cost;
				edge.included_stk.push(a);
				new_from_edges.push(edge);
			}
			nodes[a].overnode = nodes.size();
			a = nodes[a].from.id;
		} while (a != s);
		nodes.push_back({ -1, false, false, new_from_edges,{} });
	}
	void unfold() {
		while (stk.size()) {
			int a = stk.top(); stk.pop();
			if (a >= n) {
				int b = nodes[a].from.included_stk.top();
				ll d = nodes[b].from.cost;
				nodes[b].from = nodes[a].from;
				nodes[b].from.cost += d;
				nodes[b].from.included_stk.pop();
			}
			else nodes[a].fin = true;
		}
	}
public:
	Chuliu_Edmonds(const vvi &lst, const vvll &cst, int start) {
		n = lst.size();
		nodes.resize(n);
		Loop(i, n) nodes[i] = { -1, false, false, priority_queue<edge_t>(),{} };
		Loop(i, n) {
			Loop(j, lst[i].size()) {
				nodes[lst[i][j]].edges.push({ i, cst[i][j], stack<int>() });
			}
		}
		root = start;
		no_mca = false;
		nodes[root].fin = nodes[root].done = true;
		Loop(i, n) {
			if (!nodes[i].fin) {
				int a = i;
				nodes[a].done = true;
				stk.push(a);
				do {
					int b;
					do {
						if (nodes[a].edges.empty()) { no_mca = true; return; }
						nodes[a].from = nodes[a].edges.top(); nodes[a].edges.pop();
						b = nodes[a].from.id;
					} while (topnode(a) == topnode(b));
					if (nodes[b].fin) unfold();
					else if (nodes[b].done) {
						contract(b);
						stk.push(nodes.size() - 1);
						a = nodes.size() - 1;
					}
					else {
						nodes[b].done = true;
						stk.push(b);
						a = b;
					}
				} while (stk.size());
			}
		}
		return;
	}
	vector<P> get_tree_idpair() {
		if (no_mca) return{};
		vector<P> ret;
		Loop(i, n) {
			if (i != root) ret.push_back({ nodes[i].from.id, i });
		}
		return ret;
	}
	ll get_weight() {
		if (no_mca) return -1;
		ll ret = 0;
		Loop(i, n) {
			if (i != root) ret += nodes[i].from.cost;
		}
		return ret;
	}
};

int main() {
	int n, m, r; cin >> n >> m >> r;
	vvi lst(n);
	vvll cst(n);
	Loop(i, m) {
		int s, t; cin >> s >> t;
		ll c; cin >> c;
		lst[s].push_back(t);
		cst[s].push_back(c);
	}
	Chuliu_Edmonds ce(lst, cst, r);
	cout << ce.get_weight() << endl;
}
