fun main() {
    val (n, m) = nextInts()
    val a = Array(n) { nextLongs() }
    if (n == 1) {
        println(0)
        return
    }
    val dp = Array(n + 1) { LongArray(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] = min + a[i][j]
            } else {
                dp[i + 1][j] = minOf(min + a[i][j] + if (i >= 1) a[i - 1][j] else 0, dp[i][j] + a[i][j])
            }
        }
    }
    println(dp[n].minOrNull())
}

fun nextInts() = readln().split(" ").map { it.toInt() }
fun nextLongs() = readln().split(" ").map { it.toLong() }