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