#include <bits/stdc++.h>
using namespace std;

inline void min_self(long long &a, long long b) {
  if (b < a) {
    a = b;
  }
}

int main() {
  iostream::sync_with_stdio(0), cin.tie(0), cout.tie(0);

  int h, w;
  cin >> h >> w;
  vector<string> grid(h);
  for (int i = 0; i < h; i++) {
    cin >> grid[i];
  }

  using P = pair<string, pair<int, int>>;
  priority_queue<P, vector<P>, greater<P>> que;
  auto Push = [&](string s, int i, int j) {
    que.push(make_pair(s, make_pair(i, j)));
  };
  Push("", 0, 0);
  while (true) {
    auto [s, p] = que.top();
    auto [i, j] = p;
    que.pop();
    s += grid[i][j];
    if (i == h - 1 && j == w - 1) {
      cout << s << '\n';
      return 0;
    }
    if (i + 1 < h) {
      Push(s, i + 1, j);
    }
    if (j + 1 < w) {
      Push(s, i, j + 1);
    }
  }

  return 0;
}