#include <bits/stdc++.h>
using namespace std;
//#pragma GCC optimize("Ofast,O3,unroll-loops")
#define int long long
#define vi vector<int>
#define vvi vector<vi>
#define pii pair<int, int>
#define vpi vector<pii>
#define vvpi vector<vpi>
#define vb vector<bool>
#define vvb vector<vb>
#define endl "\n"
#define sp << " " <<
#define F(i, s, n) for(int i = s; i < n; i++)
#define pb push_back
#define fi first
#define se second
const int mod = 1e8;
int inf = LLONG_MAX >> 4;
int add(int x, int y) {
return (x + y) % mod;
}
int mult(int x, int y) {
return ((x % mod) * (y % mod)) % mod;
}
void solve() {
int n, m;
cin >> n >> m;
vector<string> grid(n);
F(i, 0, n) cin >> grid[i];
string dp[n][m];
dp[0][0] = string(1, grid[0][0]);
F(i, 0, n) {
F(j, 0, m) {
if(i == 0 && j == 0) continue;
if(i == 0) dp[i][j] = dp[i][j-1];
else if(j == 0) dp[i][j] = dp[i-1][j];
else dp[i][j] = min(dp[i-1][j], dp[i][j-1]);
dp[i][j] += grid[i][j];
}
}
cout << dp[n-1][m-1] << endl;
}
void setIO() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef Local
freopen("local.in", "r", stdin);
freopen("local.out", "w", stdout);
#else
//freopen("snakes.in","r",stdin);
//freopen("snakes.out","w",stdout);
#endif
}
signed main() {
setIO();
int t = 1;
//cin >> t;
while(t--) solve();
}
