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#include <stdlib.h>
//---===---
#include <stdio.h>
#include <unistd.h>

typedef unsigned int uint;

char buf_in[4096000];
int buf_in_head = 0;
int buf_in_tail = 0;

static int getChar(void) {
  while (buf_in_head == buf_in_tail) {
    int rv = read(0, buf_in, sizeof(buf_in));
    if (rv > 0) {
      buf_in_head = 0;
      buf_in_tail = rv;
      break;
    };
    if (rv == 0) return EOF;
  }
  return buf_in[buf_in_head++];
}

// only 1 call is safe, and only if previously getChar() had been called.
static void ungetChar(void) {
  --buf_in_head;
}

static uint getUInt() {
  uint v;
  int c;
  for (;;) {
    c = getChar();
    if (c < '0') continue;
    if (c > '9') continue;
    v = c - '0';
    break;
  };
  for (;;) {
    c = getChar();
    if (c < '0') break;
    if (c > '9') break;
    v *= 10;
    v += c - '0';
  };
  ungetChar();
  return v;
}
//---===---

#define INF 1222333444

#define C2000 2048
int n;

// 0 <= i <= j < n
// 1 <= c[i][j] <= 1,000,000,000
int c[C2000][C2000]; // 16 MB

int join(int i, int j) {
  return -i * C2000 - j -1;
}

int first(int v) {
  return (-v-1) / C2000;
}

int second(int v) {
  return (-v-1) % C2000;
}

int find_min(void) {
  int i, j;
  int m = INF, k = 0;

  for (i = 0; i < n; ++i) {
    for (j = i; j < n; ++j) {
      if (c[i][j] <= 0) continue;
      if (c[i][j] > m) continue;
      m = c[i][j];
      k = join(i, j);
    };
  };
  return k;
}

int lookup(int i, int j) {
  int a = i;
  int b = j;
  int w = join(a, b);

  for (;;) {
    int v = c[a][b];
    if (v >= 0) break;
    a = first(v);
    b = second(v);
    w = v;
  };
// w == join(a,b) ---> ultimate parent
  for (;;) {
    int v = c[i][j];
    if (v >= 0) break;
    c[i][j] = w;
    i = first(v);
    j = second(v);
  };
  return w;
};

void resolve(int i1, int j1, int i2, int j2) {
  int ij1, v1, ij2, v2;
  ij1 = lookup(i1, j1);
  i1 = first(ij1);
  j1 = second(ij1);
  v1 = c[i1][j1];
  ij2 = lookup(i2, j2);
  i2 = first(ij2);
  j2 = second(ij2);
  v2 = c[i2][j2];
  if (ij1 == ij2) return;
  if (v1 == 0) if (v2 == 0) return;
  if (v1 == 0) { c[i2][j2] = ij1; return; };
  if (v2 == 0) { c[i1][j1] = ij2; return; };
  if (v1 < v2) {
    c[i2][j2] = ij1;
  } else {
    c[i1][j1] = ij2;
  };
}

typedef struct {
  int i, j, c;
} tt;

tt T[C2000 * C2000 / 2]; // 24 MB
int cnt = 0;

int cmp(const tt * a, const tt * b) {
  if (a->c < b->c) return -1;
  if (a->c > b->c) return +1;
  if (a->i < b->i) return -1;
  if (a->i > b->i) return +1;
  if (a->j < b->j) return -1;
  if (a->j > b->j) return +1;
  return 0;
};

int void_cmp(const void * a, const void * b) {
  return -cmp((const tt*)a, (const tt*)b);
}

int main (void) {
  int i, j;
  long long sum = 0;

  // 1 <= n <= 2000
  //scanf("%d", &n);
  n = getUInt();

  for (i = 0; i < n; ++i) {
    for (j = i; j < n; ++j) {
      int v;
      //scanf("%d", &v);
      v = getUInt();
      c[i][j] = v;
      T[cnt].i = i;
      T[cnt].j = j;
      T[cnt].c = v;
      ++cnt;
    };
  };

// liczymy na to ze to nie ja pisalem testy
  qsort(T, cnt, sizeof(tt), void_cmp);

  for (i = 0; i < n; ++i) {
    int a, b;
    //int v = find_min();
    //a = first(v);
    //b = second(v);

    --cnt;
    a = T[cnt].i;
    b = T[cnt].j;
    //printf("%d,%d -> %d <=0 or ==%d\n", a,b, c[a][b], T[cnt].c);
    if (c[a][b] <= 0) { --i; continue; };

    //printf("%d @ %d,%d\n", c[a][b], a, b);
    sum += c[a][b];
    c[a][b] = 0;
    for (j = a; j < b; ++j) {
      //printf("%d,%d -- %d,%d\n", a,j, j+1,b);
      resolve(a,j, j+1,b);
    };
    for (j = a-1; j >= 0; --j) {
      //printf("%d,%d =- %d,%d\n", j,a-1, j,b);
      resolve(j,a-1, j,b);
    };
    for (j = b+1; j < n; ++j) {
      //printf("%d,%d -= %d,%d\n", a,j, b+1,j);
      resolve(a,j, b+1,j);
    };
    //putchar('\n');
  };
  printf("%lld\n", sum);

  return 0;
}