Go: package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
)

var (
	n int
	M [MAX][MAX]int
)

const MAX = 100
const WHITE = 0
const GRAY = 1
const BLACK = 2

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Scan()
	n, _ = strconv.Atoi(sc.Text())

	for i := 0; i < n; i++ {
		for j := 0; j < n; j++ {
			sc.Scan()
			c, _ := strconv.Atoi(sc.Text())
			if c != -1 {
				M[i][j] = c
			} else {
				M[i][j] = math.MaxInt64
			}

		}
	}
	prim()
}

func prim() {
	var u int
	var minv int
	var d [MAX]int
	var p [MAX]int
	var color [MAX]int

	for i := 0; i < n; i++ {
		d[i] = math.MaxInt64
		p[i] = -1
		color[i] = WHITE
	}

	d[0] = 0

	for {
		minv = math.MaxInt64
		u = -1
		for i := 0; i < n; i++ {
			if minv > d[i] && color[i] != BLACK {
				u = i
				minv = d[i]
			}
		}

		if u == -1 {
			break
		}

		color[u] = BLACK

		for v := 0; v < n; v++ {
			if color[v] != BLACK && M[u][v] != math.MaxInt64 {
				if d[v] > M[u][v] {
					d[v] = M[u][v]
					p[v] = u
					color[v] = GRAY
				}
			}
		}
	}
	sum := 0
	for i := 0; i < n; i++ {
		if p[i] != -1 {
			sum += M[i][p[i]]
		}
	}
	fmt.Println(sum)

}

C++: /**
 * @brief Prim?????¢?????´????????????????????????????????????
 * @note  ??¢??£URL: http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_12_A
 * @date  2016/04/17~2017/01/03
 */



//********************************************************************************
// ???????????????????????????????????????????????????
//********************************************************************************

#include <utility>
#include <algorithm>
#include <vector>
#include <tuple>
#include <iostream>



//********************************************************************************
// ???????????§????????¢?????????????????????
//********************************************************************************

#define GRAPH_BEGIN namespace graph {
#define GRAPH_END   }



//********************************************************************************
// ????????????????§????
//********************************************************************************

GRAPH_BEGIN



//********************************************************************************
// ???????????????
//********************************************************************************

using weight_t   = std::int32_t;  /**< ???(u, v)????????????w?????¨?????? */
using index_t    = std::int32_t;  /**< ??????v??????????????¨??????       */
using capacity_t = weight_t;      /**< ???(u, v)??????????????¨??????    */
using bool_t     = std::int32_t;  /**< ?????????????????´??°?????§???{ false 0 true ????????\??? }??¨?????? */



//********************************************************************************
// ?§????????????????
//********************************************************************************

/**
 * @brief  ????????????????§???????(scoped enum)
 * @detail (u, v) ??? E??§??????u??????????????°??????v?????°????????§??????
 *         ?????????????????????????????£??\????????¨?????????????????????????????§??????
 *         ??°???????????????????????£??\???????????¨???????????????????????????????????¢??????????????¨???????????????????¢?????????????
 */
enum struct vcolor : std::int32_t {
    white,  /**< ??????????????? */
    black,  /**< ??¢???????????? */
    gray,   /**< ??¢???????????? */
};

/**
 * @brief ??°????????¨?????????(??????) 
 */
struct vertex {
    union {
        weight_t d;       /**< ?§????s??????????????¢  */
        weight_t key;     /**< Prim?????¢?????´???????????????????????¨????±?????????????????????¨????????¶?????? */
    };
    index_t pi;           /**< ????????????(?????????) */
    union {
        vcolor color;     /**< ????????????        */
        bool_t  visited;  /**< ????????????????     */
    };
    // weight_t f;           /**< ??????????????°(DFS?????????????????????????????????????????¨??????????????????)     */
    vertex() noexcept : d(0), pi(0), color(vcolor::white)/*, f(0)*/ {}
};

/**
 * @brief ??°????????¨??¨??????(???)
 * @note  G = (V, E)???????????¢??°w???????????????????????°????????¨????????¨???
 *        ???(u, v) ??? E????????????w(u, v)??¨??¨?????????
 */
struct edge {
    index_t  src;   /**< ???????§????u */
    index_t  dst;   /**< ????????????v */
    union {
        weight_t w;     /**< ???(u, v)????????????(?????????) */
        capacity_t c;   /**< ???(u, v)????????? */
    };
    edge() = default;
    edge(index_t src, index_t dst) noexcept             : src(src), dst(dst), w(1) {}
    edge(index_t src, index_t dst, weight_t w) noexcept : src(src), dst(dst), w(w) {}
};



namespace limits {
    enum {  // scoped??§????????????????????????????????????enum(strongly-typed enum)??§?????????
        inf = std::numeric_limits<weight_t>::max() / 3,  /**< @brief ???????????¨???????????´???????????¨????????????     */
        nil = std::numeric_limits<index_t>::min() / 3,   /**< @brief ?????????????????¨???????????´???????????¨???????????? */
    };
}



//********************************************************************************
// ?????????????????????2
//********************************************************************************

using edges_t    = std::vector<edge>;      /**< ??°??????G=(V, E)????????????E   */
using vertices_t = std::vector<vertex>;    /**< ??°??????G=(V, E)???????????????V */
using array_t    = std::vector<weight_t>;  /**< ??????w?????????  */
using indices_t  = std::vector<index_t>;   /**< ????????????????????? */
using stamps_t   = std::vector<bool_t>;    /**< ???????????¢???????????? */
using matrix_t   = std::vector<array_t>;   /**< ??°??????G?????£??\????????¨???(???????????¨????????¨???) */
using graph_t    = std::vector<edges_t>;   /**< ??°??????G?????£??\???????????¨???(???????????????????????¨??????) */



//********************************************************************************
// ??¢??°?????????
//********************************************************************************

/**
 * @brief  Prim?????¢?????´???????????????????????????????°???¨?????¨A????±?????????????????????????(A????????¨??\?¶??????????????????????)?????£???????????????????????¢??????
 *         Dijkstra?????¢?????´????????????????????????????§????s?????????????°???????????????¨?????????????????????u ??? V - S???????????????(??????S????±??????????"????????????"??????????±???????)
 *
 * @note   ????????¢??°???????????????????????????Heap???????????????Prim?????????Dijkstra?????¢?????´???????????§?????????
 *         ????????§??????Heap?????¨???????????§min????????????????????\????????????????????????
 *         ?????????????????¢?????´?????????????¨???°??????????????????????????????????????????????????????????????°?????????????????¨????????????
 *         ?????£??????v.visited???false?????¨??????v.color?????????????????°?????§?????????true?????¨??????????????§??????
 *
 * @param  const vertices_t& V ??¢?´¢????±????????????????V
 * @param  index_t n           ????????????V???????????°n
 * @return index_t u           ?????¶??????????????????u(?????¶??????????????????????????¨???????????´??????nil?????????)
 */
static index_t extract_min(const vertices_t& V, index_t n)
{
    index_t  u = limits::nil;
    weight_t d = limits::inf; 
    for (index_t v = 0; v < n; ++v) {
        if (!V[v].visited && V[v].d < d) { d = V[v].d; u = v; }
    }
    return u;
}


/**
 * @brief  Prim?????¢?????´?????????
 *
 * @note   Prim?????¢?????´?????????????????°??????????????????????±???????Dijkstra?????¢?????´???????????¨?????¨?????????????????????????????????
 *         Prim?????¢?????´??????????????????A???????????????1????????¨?????¢???????????¨????????§????????????. ????????¨???????????????r??????????§???????V???????????¨?????????????????§????????????
 *         ?????????????????§??????A???????????¨???????????????(A????????¨??\?¶??????????????????????)?????£???????????????????????¨A????????????
 *         A?????????????????¨???????????????????????????????????£???A?????????????????????????????¢?????´??????????????????????????¨??????A?????????????°???¨?????¨?????¢?????????
 *         ?????????????????§?????¨?????????????¢????????????????????°????????????????????????¨????????¨???????????????????????§????????????????¬??????\??§??????
 *
 * @note   ??????v????±???§v.key???v??¨??¨????±?????????????????????¨????????¶??????????°?????????§??????. ??????????????????????????????????????¨??????????????°???v.key = ?????¨????????????
 *         ?±???§v.???????¨????????????v???????????????
 *
 * @note   ??°??????G = (V, E)?????£??\??????????????£????????????????????¨????????(V^2)??§??°???Prim?????¢?????´??????????????\???????????????????????§??????
 * 
 * @param  const matrix_t& W ??£??\??????W
 * @param  index_t         r ????°???¨?????¨??????
 */
std::pair<vertices_t, weight_t> prim(const matrix_t& W, index_t r)
{
    index_t n = W.size();
    vertices_t A(n); weight_t w;

    
    for (auto&& u : A) {
        u.key = limits::inf;  // ????????????????????????????¨??????????
        u.pi  = limits::nil;  // ??????????????????NIL????¨??????????
        u.visited = false;
    }
    A[r].key = w = 0;         // ???r???????????§????????????????????????????????????????????????0????¨??????????
    while (true) {
        // ????°???¨?????¨A????±?????????????????????????(A????????¨??\?¶??????????????????????)?????£???????????????????????¢???
        index_t u = extract_min(A, n);
        if (u == limits::nil) { break; }   // ??????u???NIL?????????????????°?????¢?´¢???????????§?????????????°???¨?????¨A??? A = {(v, v.??) : v ??? V - { r } }??§??????
        for (index_t v = 0; v < n; ++v) {  // ??????u?????£??\???????????°????????????
            if (W[u][v] < A[v].key) {      // ?????????????????°?????????????????????????±???§?????´??°?¢????????????????????????????
                A[v].pi  = u;              // v??????±???§??¨
                A[v].key = W[u][v];        // key?±???§?????´??°??????
            }
        }
        A[u].visited = true;  // ???(u, u.??)???????°???¨?????¨A????????????(???????????????r?????????)
        w += A[u].key;        // ????°????????????´??°
    }
    return std::make_pair(A, w);
}



//********************************************************************************
// ?????????????????????
//********************************************************************************

GRAPH_END



//********************************************************************************
// ??¨?????????????????????
//********************************************************************************


int main(void)
{
    using namespace graph;
    using namespace std;
    matrix_t M;
    int n, k;
    
    cin >> n; M.resize(n);
    for (int j = 0; j < n; j++) {
        M[j].resize(n);
        for (int i = 0; i < n; i++) {
            cin >> k;
            M[j][i] = k == -1 ? limits::inf : k;
        }
    }

    auto mst = prim(M, 0);
    cout << mst.second << endl;
    
    return 0;
}