mod = 998244353
inf = 10 ** 17


def main():
    import sys
    input = sys.stdin.readline

    N, M = map(int, input().split())
    A = []
    for _ in range(N):
        A.append(list(map(int, input().split())))
    
    if N == 1:
        print(0)
        exit()

    dp = A[0][:]
    mi = min(dp)
    for i in range(1, N):
        dp_new = [inf] * M
        for j in range(M):
            dp_new[j] = min(dp[j] + A[i][j], mi + A[i][j] + A[i-1][j])
        dp = dp_new
        mi = min(dp)
    print(mi)


if __name__ == '__main__':
    main()