import std.algorithm, std.conv, std.range, std.stdio, std.string; alias Point!int point; alias Grid!(int, int) grid; const dirs = [point(1, 0), point(0, 1), point(-1, 0), point(0, -1)]; void main() { auto n = readln.chomp.to!size_t; auto g = grid(n, n), c = 1, p = point(0, 0), d = 0; while (c <= n*n) { g[p] = c++; auto np = p + dirs[d]; if (!g.validPoint(np) || g[np]) { d = (d + 1) % 4; np = p + dirs[d]; } p = np; } foreach (i; 0..n) { foreach (j; 0..n) { writef("%03d", g[i][j]); if (j < n-1) write(" "); } writeln; } } struct Point(T) { T x, y; pure auto opBinary(string op: "+")(Point!T rhs) const { return Point!T(x + rhs.x, y + rhs.y); } pure auto opBinary(string op: "-")(Point!T rhs) const { return Point!T(x - rhs.x, y - rhs.y); } } struct Grid(T, U) { import std.algorithm, std.conv, std.range, std.traits, std.typecons; const sibs4 = [Point!U(-1, 0), Point!U(0, -1), Point!U(1, 0), Point!U(0, 1)]; const sibs8 = [Point!U(-1, 0), Point!U(-1, -1), Point!U(0, -1), Point!U(1, -1), Point!U(1, 0), Point!U(1, 1), Point!U(0, 1), Point!U(-1, 1)]; T[][] m; const size_t rows, cols; mixin Proxy!m; this(size_t r, size_t c) { rows = r; cols = c; m = new T[][](rows, cols); } this(T[][] s) { rows = s.length; cols = s[0].length; m = s; } pure auto dup() const { return Grid(m.map!(r => r.dup).array); } ref pure auto opIndex(Point!U p) { return m[p.y][p.x]; } ref pure auto opIndex(size_t y) { return m[y]; } ref pure auto opIndex(size_t y, size_t x) const { return m[y][x]; } static if (isAssignable!T) { auto opIndexAssign(T v, Point!U p) { return m[p.y][p.x] = v; } auto opIndexAssign(T v, size_t y, size_t x) { return m[y][x] = v; } auto opIndexOpAssign(string op, V)(V v, Point!U p) { return mixin("m[p.y][p.x] " ~ op ~ "= v"); } auto opIndexOpAssign(string op, V)(V v, size_t y, size_t x) { return mixin("m[y][x] " ~ op ~ "= v"); } } pure auto validPoint(Point!U p) { return p.x >= 0 && p.x < cols && p.y >= 0 && p.y < rows; } pure auto points() const { return rows.to!U.iota.map!(y => cols.to!U.iota.map!(x => Point!U(x, y))).joiner; } pure auto sibPoints4(Point!U p) { return sibs4.map!(s => p + s).filter!(p => validPoint(p)); } pure auto sibPoints8(Point!U p) { return sibs8.map!(s => p + s).filter!(p => validPoint(p)); } }