import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
#import bisect
#import itertools
#import random
#from heapq import heapify, heappop, heappush
#from collections import defaultdict 
#from collections import deque
#import copy #DeepCopy: hoge = [_[:] for _ in hogehoge]
#import math
#from functools import lru_cache
#@lru_cache(maxsize=None)
#MOD = pow(10,9) + 7
MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

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

    dp = ['']*W
    for i in range(H):
        p = ['']*W
        p,dp = dp,p
        for j in range(W):
            if i == 0 and j == 0:
                dp[0] = S[0][0]
            elif j == 0:
                dp[j] = p[j] + S[i][j]
            elif i == 0:
                dp[j] = dp[j-1] + S[i][j]
            else:
                dp[j] = min(p[j], dp[j-1]) + S[i][j]
        # print(dp)

    print(dp[-1]) 
                

if __name__ == '__main__':
    main()