import sys
input=lambda:sys.stdin.readline().rstrip()
def compare(a,b):
	return a if a<b else b
H,W=map(int,input().split())
S=[input() for i in range(H)]
dp=[['' for i in range(W)] for j 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 i in range(W-2,-1,-1):
	dp[H-1][i]=S[H-1][i]+dp[H-1][i+1]
for i in range(H-2,-1,-1):
	for j in range(W-2,-1,-1):
		dp[i][j]=S[i][j]+compare(dp[i+1][j],dp[i][j+1])
print(dp[0][0])