package main

import . "fmt"
import . "os"
import bf "bufio"
import . "slices"

func main() {
	rd := bf.NewReader(Stdin)
	var n, m int
	Fscan(rd, &n, &m)
	if n == 1 {
		Println(0)
		return
	}
	a := make([][]int, n)
	for i := range a {
		a[i] = make([]int, m)
		for j := range a[i] {
			Fscan(rd, &a[i][j])
		}
	}
	dp := make([]int, m)
	for i := range dp {
		dp[i] = a[0][i] + a[1][i]
	}
	for i := 1; i < n-1; i++ {
		tmp := make([]int, m)
		e := Min(dp)
		for j, v := range dp {
			tmp[j] = min(e + a[i][j], v) + a[i+1][j]
		}
		dp = tmp
	}
	Println(Min(dp))
}