H,W = map(int,input().split())
S = [input() for _ in range(H)]

dp = [[None] * W for _ in range(H)]
dp[0][0] = S[0][0]
for h in range(H):
    for w in range(W):
        if h == 0 and w == 0:continue
        t = None
        s = None
        if h > 0:
            t = dp[h-1][w] + S[h][w]
        if w > 0:
            s = dp[h][w-1] + S[h][w]
        if t is None:
            dp[h][w] = s
        elif s is None:
            dp[h][w] = t
        else:
            dp[h][w] = min(t,s)
print(dp[-1][-1])