#include<bits/stdc++.h> using namespace std; char a[35][35]; string answer; long double f[65]; long double n, m, k; long double fact (int a) { if (a <= 1) return 1; if (f[a]) return f[a]; return f[a] = a * fact(a-1); } long double ways (int i, int j) { return ( fact(n-i+m-j) / fact(m-j) ) / fact(n-i); } void ans (int i = 1, int j = 1) { if (i == n) { for (int x = j; x <= m; x++) answer += a[i][x]; return; } if (j == m) { for (int x = i; x <= n; x++) answer += a[x][j]; return; } // cerr << ways(i+1, j) << ' ' << ways(i, j+1) << ' ' << k << endl; answer += a[i][j]; if (a[i+1][j] < a[i][j+1]) { if (ways(i+1, j) >= k) return ans(i+1, j); k-=ways(i+1, j); return ans(i, j+1); } else { if (ways(i, j+1) >= k) return ans(i, j+1); k-=ways(i, j+1); return ans (i+1, j); } } int main(){ ios_base::sync_with_stdio(false); cin.tie(NULL); cin >> n >> m; for (int i = 1; i <= n; i++) { for (int j = 1; j <= m; j++) { cin >> a[i][j]; } } cin >> k; ans(); cout << answer; return 0; } /* POSSIBLE BUGS overflow */ /* TESTCASE */