#define _GLIBCXX_DEBUG
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std; using ll = long long; using pii = pair<int, int>; using pll = pair<ll, ll>; using pdd = pair<double, double>; using pss = pair<string, string>; using pcc = pair<char, char>; using pbb = pair<bool, bool>; using pil = pair<int, ll>; using pli = pair<ll, int>; using ti3 = tuple<int, int, int>; using tl3 = tuple<ll, ll, ll>; using td3 = tuple<double, double, double>; using ts3 = tuple<string, string, string>; using tc3 = tuple<char, char, char>; using tb3 = tuple<bool, bool, bool>; using ti4 = tuple<int, int, int, int>; using tl4 = tuple<ll, ll, ll, ll>; using td4 = tuple<double, double, double, double>; using ts4 = tuple<string, string, string, string>; using tc4 = tuple<char, char, char, char>; using tb4 = tuple<bool, bool, bool, bool>; using vi = vector<int>; using vl = vector<ll>; using vd = vector<double>; using vs = vector<string>; using vc = vector<char>; using vb = vector<bool>; using vvi = vector<vi>; using vvl = vector<vl>; using vvd = vector<vd>; using vvs = vector<vs>; using vvc = vector<vc>; using vvb = vector<vb>; using vvvi = vector<vvi>; using vvvl = vector<vvl>; using vvvd = vector<vvd>; using vvvs = vector<vvs>; using vvvc = vector<vvc>; using vvvb = vector<vvb>; using vpii = vector<pii>; using vpll = vector<pll>; using vpdd = vector<pdd>; using vpss = vector<pss>; using vpcc = vector<pcc>; using vpbb = vector<pbb>; using vpil = vector<pil>; using vpli = vector<pli>; using vti3 = vector<ti3>; using vtl3 = vector<tl3>; using vtd3 = vector<td3>; using vts3 = vector<ts3>; using vtc3 = vector<tc3>; using vtb3 = vector<tb3>; using vti4 = vector<ti4>; using vtl4 = vector<tl4>; using vtd4 = vector<td4>; using vts4 = vector<ts4>; using vtc4 = vector<tc4>; using vtb4 = vector<tb4>; using mii = map<int, int>; using mll = map<ll, ll>; using msi = map<string, int>; using mci = map<char, int>; using mil = map<int, ll>; using mli = map<ll, int>; using si = set<int>; using sl = set<ll>; using sd = set<double>; using ss = set<string>; using sc = set<char>; using sb = set<bool>; using spii = set<pii>; using spll = set<pll>; using spdd = set<pdd>; using spss = set<pss>; using spcc = set<pcc>; using spbb = set<pbb>; using spil = set<pil>; using spli = set<pli>; using sti3 = set<ti3>; using stl3 = set<tl3>; using std3 = set<td3>; using sts3 = set<ts3>; using stc3 = set<tc3>; using stb3 = set<tb3>;
#define rep0(TMS) for (int CNT = 0; CNT < (int)(TMS); CNT++)
#define rep(CNT, GOAL) for (int CNT = 0; CNT < (int)(GOAL); CNT++)
#define rep2(CNT, START, GOAL) for (int CNT = (int)(START); CNT < (int)(GOAL); CNT++)
#define rep3(CNT, START, GOAL) for (int CNT = (int)(START); CNT > (int)(GOAL); CNT--)
#define all(CONT) begin(CONT), end(CONT)
#define fr1(CONT) next(begin(CONT)), end(CONT)
#define itrep(ITR, CONT) for (auto ITR = begin(CONT); ITR != end(CONT); ITR++)
#define itrep1(ITR, CONT) for (auto ITR = next(begin(CONT)); ITR != end(CONT); ITR++)
#define maxel(CONT) *max_element(all(CONT))
#define minel(CONT) *min_element(all(CONT))
template <typename T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; }
template <typename T> bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; }
template <typename T> T sum(const vector<T> &VEC) { return accumulate(all(VEC), 0.0); }
template <typename T> vector<T> acm(const vector<T> &VEC) { vector<T> RES(VEC.size() + 1); rep(CNT, VEC.size()) RES[CNT + 1] = RES[CNT] + VEC[CNT]; return RES; }
template <typename T> void fil(vector<T> &VEC, const int NUM, const T &VAL) { VEC.assign(NUM, VAL); }
template <typename T> void fil(vector<T> &VEC, const int NUM) { VEC.assign(NUM, 0.0); }
template <typename T> void fil(vector<vector<T>> &VV, const int RNUM, const int CNUM, const T &VAL) { fil(VV, RNUM, vector<T>()); rep(CNT, RNUM) fil(VV[CNT], CNUM, VAL); }
template <typename T> void fil(vector<vector<T>> &VV, const int RNUM, const int CNUM) { fil(VV, RNUM, vector<T>()); rep(CNT, RNUM) fil(VV[CNT], CNUM); }
template <typename T> void fil(vector<vector<T>> &VV, const int RNUM) { fil(VV, RNUM, vector<T>()); }
void prec(const int &DIG) { cerr << fixed << setprecision(DIG); cout << fixed << setprecision(DIG); }
template <typename T> void COUT(const T &ELEM) { cout << ELEM; }
template <typename T> void pout(const T &ELEM) { COUT(ELEM); cout << " "; }
template <typename T, typename ...Ts> void pout(const T &FIRST, const Ts &...REST) { pout(FIRST); pout(REST...); }
template <typename T> void print(T ELEM) { COUT(ELEM); cout << "\n"; }
template <typename T, typename ...Ts> void print(const T &FIRST, const Ts &...REST) { print(FIRST); print(REST...); }
void CERR() { cerr << "\n"; }
template <typename T> void CERR(const T &ELEM) { cerr << ELEM; }
template <typename T, typename ...Ts> void CERR(const T &FIRST, const Ts &...REST) { CERR(FIRST); cerr << ", "; CERR(REST...); }
template <typename T1, typename T2> void CERR(const pair<T1, T2> &PAIR) { cerr << "("; CERR(PAIR.first); cerr << ", "; CERR(PAIR.second); cerr << ")"; }
template <typename T1, typename T2, typename T3> void CERR(const tuple<T1, T2, T3> &TUP3) { cerr << "("; CERR(get<0>(TUP3)); cerr << ", "; CERR(get<1>(TUP3)); cerr << ", "; CERR(get<2>(TUP3)); cerr << ")"; }
template <typename T1, typename T2, typename T3, typename T4> void CERR(const tuple<T1, T2, T3, T4> &TUP4) { cerr << "("; CERR(get<0>(TUP4)); cerr << ", "; CERR(get<1>(TUP4)); cerr << ", "; CERR(get<2>(TUP4)); cerr << ", "; CERR(get<3>(TUP4)); cerr << ")"; }
template <typename T> void CERR(const vector<T> &VEC) { cerr << "{ "; itrep(ITR, VEC) { CERR(*ITR); cerr << ", "; } cerr << "}"; }
template <typename T> void CERR1(const vector<T> &VEC) { cerr << "{ "; itrep1(ITR, VEC) { CERR(*ITR); cerr << ", "; } cerr << "}"; }
template <typename T> void CERR(const set<T> &SET) { cerr << "{ "; itrep(ITR, SET) { CERR(*ITR); cerr << ", "; } cerr << "}"; }
template <typename T1, typename T2> void CERR(const map<T1, T2> &MAP) { cerr << "{ "; itrep(ITR, MAP) { CERR(*ITR); cerr << ", "; } cerr << "}"; }
#define db(OBJ) cerr << #OBJ << ": "; CERR(OBJ); cerr << ", "
#define dbl(OBJ) cerr << #OBJ << ": "; CERR(OBJ); cerr << "\n"
#define db1(OBJ) cerr << #OBJ << ": "; CERR1(OBJ); cerr << "\n"
#define dbs(...) cerr << "(" << #__VA_ARGS__ << "): ("; CERR(__VA_ARGS__); cerr << ")\n"
#define dbvv(VV) cerr << #VV << ": {\n"; rep(CNT, VV.size()) { cerr << #VV << "[" << CNT << "]: "; CERR(VV[CNT]); cerr << ",\n"; } cerr << "}\n"
#define db01(VV) cerr << #VV << ": {\n"; rep(CNT, VV.size()) { cerr << #VV << "[" << CNT << "]: "; CERR1(VV[CNT]); cerr << ",\n"; } cerr << "}\n"
#define db10(VV) cerr << #VV << ": {\n"; rep2(CNT, 1, VV.size()) { cerr << #VV << "[" << CNT << "]: "; CERR(VV[CNT]); cerr << ",\n"; } cerr << "}\n"
#define db11(VV) cerr << #VV << ": {\n"; rep2(CNT, 1, VV.size()) { cerr << #VV << "[" << CNT << "]: "; CERR1(VV[CNT]); cerr << ",\n"; } cerr << "}\n"
#define YN(FLG) cout << (FLG ? "YES" : "NO") << "\n"
#define Yn(FLG) cout << (FLG ? "Yes" : "No") << "\n"
#define yn(FLG) cout << (FLG ? "yes" : "no") << "\n"
#define pcase(NUM) cout << "Case #" << NUM << ":" << " "
#define pcasel(NUM) cout << "Case #" << NUM << ":" << "\n"
// const ll INF = 1'000'000'000'000'000'007;
const int INF = 1'000'000'007;
const ll MOD = 998'244'353;

vi par, dep, siz;
int root(int x) {
	if (par[x] == x) return x;
	else return par[x] = root(par[x]);
}
void unite(int x, int y) {
	x = root(x); y = root(y);
	if (x == y) return;
	if (dep[x] > dep[y]) { par[y] = x; siz[x] += siz[y]; }
	else if (dep[x] < dep[y]) { par[x] = y; siz[y] += siz[x]; }
	else { par[y] = x; dep[x] ++; siz[x] += siz[y]; }
}
bool same(int x, int y) { return root(x) == root(y); }
void uf(int NODENUM) {
	par.assign(NODENUM, 0); dep.assign(NODENUM, 0); siz.assign(NODENUM, 1);
	rep(i, NODENUM) par[i] = i;
}
ll kruskal(vector<vpil> cg) {
	using tlii = tuple<ll, int, int>;
	priority_queue<tlii, vector<tlii>, greater<tlii>> pq;
	rep(u, cg.size()) {
		for (pil p : cg[u]) {
			int v; ll d; tie(v, d) = p;
			pq.push(tlii(d, u, v));
		}
	}
	uf(cg.size());
	int cnt = 0; ll dsum = 0;
	while (cnt < cg.size() - 1) {
		int u, v; ll d; tie(d, u, v) = pq.top(); pq.pop();
		if (!same(u, v)) {
			unite(u, v);
			dsum += d;
			cnt++;
		}
	}
	return dsum;
}
ll kruskal(vvi g, vvl dis) {
	vector<vpil> cg(g.size());
	rep(u, g.size()) for (int v : g[u]) cg[u].push_back(pil(v, dis[u][v]));
	return kruskal(cg);
}

int main() {
	// 0-ind
	int n; cin >> n;
	vector<vpil> cg(n);
	rep(i, n) {
		rep(j, n) {
			ll a; cin >> a;
			if (a != -1) cg[i].push_back(make_pair(j, a));
		}
	}
	print(kruskal(cg));
}


Measured memory_bytes: 3320