import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		int m = Integer.parseInt(sa[1]);
		int[][] a = new int[n][m];
		for (int i = 0; i < n; i++) {
			sa = br.readLine().split(" ");
			for (int j = 0; j < m; j++) {
				a[i][j] = Integer.parseInt(sa[j]);
			}
		}
		br.close();

		if (n == 1) {
			System.out.println(0);
			return;
		}

		long inf = 2000000000000000000L;
		long[][] dp = new long[n][m];
		for (int i = 0; i < m; i++) {
			dp[0][i] = a[0][i];
		}
		for (int i = 1; i < n; i++) {
			long[] minL = new long[m + 1];
			minL[0] = inf;
			for (int j = 0; j < m; j++) {
				minL[j + 1] = Math.min(minL[j], dp[i - 1][j]);
			}

			long[] minR = new long[m + 1];
			minR[m] = inf;
			for (int j = m - 1; j >= 0; j--) {
				minR[j] = Math.min(minR[j + 1], dp[i - 1][j]);
			}

			for (int j = 0; j < m; j++) {
				long v0 = dp[i - 1][j] + a[i][j];
				long v1 = minL[j] + a[i - 1][j] + a[i][j];
				long v2 = minR[j + 1] + a[i - 1][j] + a[i][j];
				dp[i][j] = Math.min(Math.min(v0, v1), v2);
			}
		}

		long ans = Long.MAX_VALUE;
		for (int i = 0; i < m; i++) {
			ans = Math.min(ans, dp[n - 1][i]);
		}
		System.out.println(ans);
	}
}