import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val n = nextInt()
    val m = nextInt()
    val a = Array(n) { Array(m) { nextLong() } }
    if (n == 1) {
        println(0)
        return
    }
    val dp = Array(n + 1) { Array(m) { Long.MAX_VALUE / 2 } }
    for (i in 0 until m) {
        dp[0][i] = 0
    }
    for (i in 0 until n) {
        val min = dp[i].minOrNull()!!
        for (j in 0 until m) {
            if (dp[i][j] == min) {
                dp[i + 1][j] = minOf(dp[i + 1][j], min + a[i][j])
            } else {
                dp[i + 1][j] = minOf(dp[i + 1][j], min + a[i][j] + if (i >= 1) a[i - 1][j] else 0, dp[i][j] + a[i][j])
            }
        }
    }
    println(dp[n].minOrNull()!!)
}

fun main() {
    Thread(null, {
        val writer = PrintWriter(System.out, false)
        writer.solve()
        writer.flush()
    }, "solve", abs(1L.shl(26)))
        .apply { setUncaughtExceptionHandler { _, e -> e.printStackTrace(); kotlin.system.exitProcess(1) } }
        .apply { start() }.join()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()
fun nextDouble() = next().toDouble()
// endregion