/* -*- coding: utf-8 -*-
 *
 * 2095.cc:  No.2095 High Rise - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_M = 1000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N][MAX_M];
ll dp[MAX_N + 1][MAX_N];

/* subroutines */

inline void setmin(ll &a, ll b) { if (a > b) a = b; }

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  if (n == 1) { puts("0"); return 0; }

  for (int i = 0; i < n; i++)
    for (int j = 0; j < m; j++) scanf("%d", as[i] + j);

  ll mind = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      dp[i + 1][j] = dp[i][j] + as[i][j];
      if (i > 0)
	setmin(dp[i + 1][j], mind + as[i - 1][j] + as[i][j]);
    }
    mind = *min_element(dp[i + 1], dp[i + 1] + m);
  }

  printf("%lld\n", mind);

  return 0;
}