using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(int n) => Enumerable.Repeat(0, n).Select(_ => NList).ToArray();
    static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = ((int)c[0], c[1]);
        var map = NArr(n);
        if (n == 1)
        {
            WriteLine(0);
            return;
        }
        var dp = new long[n][];
        for (var i = 0; i < dp.Length; ++i) dp[i] = Enumerable.Repeat(long.MaxValue / 2, m).ToArray();
        for (var j = 0; j < m; ++j)
        {
            dp[1][j] = map[0][j] + map[1][j];
        }
        for (var i = 1; i + 1 < n; ++i)
        {
            var fpos = 0;
            var fval = long.MaxValue;
            for (var j = 0; j < m; ++j)
            {
                if (dp[i][j] < fval)
                {
                    fpos = j;
                    fval = dp[i][j];
                }
            }
            for (var j = 0; j < m; ++j)
            {
                if (fpos == j)
                {
                    dp[i + 1][j] = Math.Min(dp[i + 1][j], dp[i][j] + map[i + 1][j]);
                }
                else
                {
                    dp[i + 1][j] = Math.Min(dp[i + 1][j], dp[i][j] + map[i + 1][j]);
                    dp[i + 1][j] = Math.Min(dp[i + 1][j], dp[i][fpos] + map[i][j] + map[i + 1][j]);
                }
            }
        }
        WriteLine(dp[n - 1].Min());
    }
}