H,W = map(int,input().split())
S = [list(input()) for _ in range(H)]
dp = [[0 for _ in range(W)] for _ in range(H)]
dp[H-1][W-1] = S[H-1][W-1]
for i in range(H-2,-1,-1):
    dp[i][W-1] = S[i][W-1]+dp[i+1][W-1]
for j in range(W-2,-1,-1):
    dp[H-1][j] = S[H-1][j]+dp[H-1][j+1]
for i in range(H-2,-1,-1):
    for j in range(W-2,-1,-1):
        dp[i][j] = S[i][j]+min(dp[i+1][j],dp[i][j+1])
print(dp[0][0])