#include using namespace std; #define rep(i,n) for(int i = 0; i < (int)n; i++) #define FOR(n) for(int i = 0; i < (int)n; i++) #define repi(i,a,b) for(int i = (int)a; i < (int)b; i++) #define pb push_back #define m0(x) memset(x,0,sizeof(x)) #define fill(x,y) memset(x,y,sizeof(x)) #define bg begin() #define ed end() #define all(x) x.bg,x.ed //#define mp make_pair #define vi vector #define vvi vector #define vll vector #define vvll vector #define vs vector #define vvs vector #define vc vector #define vvc vector #define pii pair #define pllll pair #define vpii vector> #define vpllll vector> #define vpis vector> #define vplls vector> #define vpsi vector> #define vpsll vector> template void chmax(T &a, const T &b) {a = (a > b? a : b);} template void chmin(T &a, const T &b) {a = (a < b? a : b);} using ll = long long; using ld = long double; using ull = unsigned long long; const ll INF = numeric_limits::max() / 2; const ld pi = 3.1415926535897932384626433832795028; const ll mod = 1e9 + 7; int dx[] = {-1, 0, 1, 0, -1, -1, 1, 1}; int dy[] = {0, -1, 0, 1, -1, 1, -1, 1}; #define int long long void solve() { int h, w; cin >> h >> w; vector s(h); FOR(h) cin >> s[i]; pii init = {-1, -1}; vector pre(h, vpii(w, init)); vvi done(h, vi(w, false)); queue que; que.emplace(0, 0); while(que.size()) { vpii nxt; char c = s[que.front().first][que.front().second]; while(que.size()) { int x, y; tie(x, y) = que.front(); que.pop(); if(c < s[x][y]) continue; vpii nnxt; if(x != h-1 && !done[x+1][y]) { pre[x+1][y] = {x, y}; done[x+1][y] = true; nnxt.emplace_back(x+1, y); } if(y != w-1 && !done[x][y+1]) { pre[x][y+1] = {x, y}; done[x][y+1] = true; nnxt.emplace_back(x, y+1); } sort(all(nnxt), [&](pii p, pii q) { return s[p.first][p.second] < s[q.first][q.second]; }); for(auto e : nnxt) nxt.push_back(e); } for(auto e : nxt) que.push(e); } int now_x = h-1, now_y = w-1; string ans = ""; while(pre[now_x][now_y] != init) { ans.push_back(s[now_x][now_y]); tie(now_x, now_y) = pre[now_x][now_y]; } ans.push_back(s[0][0]); reverse(all(ans)); cout << ans << endl; // for(auto e : pre) { // for(auto f : e) { // cout << "{" << f.first << "," << f.second << "}" << " "; // } // cout << "\n"; // } } signed main() { cin.tie(nullptr); ios::sync_with_stdio(false); solve(); return 0; }