refactor(structure): normalize folder names with leading zeros for consistency

- Renamed all folders from format NEx (e.g., 1Ex, 2Ex...) to 0NEx (01Ex, 02Ex, etc.)
- Updated subdirectories and files accordingly
- Removed old main Makefile and tasks (a01.c–a09.c, solve.c, io_status.h), likely obsolete
- Cleaned up deprecated task binaries and configs

2025.02.21/04Ex/solve.c

@@ -0,0 +1,29 @@
+#include "solve.h"
+
+int t4_solve(char ** a, int n, char *s) {
+	size_t len_s = strlen(s);
+	int i, j, k;
+	for (i = 0, j = 0, k = 0; i < n; ++i) {
+		if (len_s <= strlen(a[i])) {
+			if (i != j) 
+			{
+				a[j] = a[i];
+			}
+			j++;
+			k = 0;
+		} else {
+			if (k == 0)  {
+				if (i != j)
+					a[j] = a[i];
+				j++;
+			} else {
+				free(a[i]);
+			}
+			k++;
+		}
+	}
+
+	for (i = j; i < n; ++i) a[i] = 0;
+
+	return j;
+}