diff --git a/crisscross.cpp b/crisscross.cpp
new file mode 100644
index 0000000..697ec77
--- /dev/null
+++ b/crisscross.cpp
@@ -0,0 +1,87 @@
+
+
+#include <iostream>
+
+int main()
+{
+  // maximum digit
+  unsigned int maxDigit = 9;
+  std::cin >> maxDigit;
+
+  // restrict variable "a"
+  bool even = (maxDigit + 1) % 2 == 0;
+  auto maxA = even ? (maxDigit - 1) / 2 : maxDigit;
+
+  unsigned int result   = 0;
+  for (unsigned int a = 0; a <= maxA; a++) // limit a to 0..4 => for every solution found there is a "inverted" version where x = 9 - x and x = a,b,c,d,...,p
+    for (unsigned int b = 0; b <= maxDigit; b++)
+      for (unsigned int c = 0; c <= maxDigit; c++)
+        for (unsigned int d = 0; d <= maxDigit; d++)
+        {
+          // all rows, columns, diagonals must share the same sum
+          auto sum = a + b + c + d;
+
+          for (unsigned int e = b; e <= maxDigit; e++) // !!! start at b instead of zero
+            for (unsigned int f = 0; f <= maxDigit; f++)
+              for (unsigned int g = 0; g <= maxDigit; g++)
+              {
+                // sum of second row must be identical to first row
+                auto h = sum - e - f - g;
+                if (h > maxDigit)
+                  continue;
+
+                for (unsigned int i = 0; i <= maxDigit; i++)
+                {
+                  // sum of first column must be identical to first row
+                  auto m = sum - a - e - i;
+                  if (m > maxDigit)
+                    continue;
+
+                  // sum of anti-diagonal must be identical to first row
+                  auto j = sum - d - g - m;
+                  if (j > maxDigit)
+                    continue;
+
+                  // sum of second column must be identical to first row
+                  auto n = sum - b - f - j;
+                  if (n > maxDigit)
+                    continue;
+
+                  for (unsigned int k = 0; k <= maxDigit; k++)
+                  {
+                    // sum of third column must be identical to first row
+                    auto o = sum - c - g - k;
+                    if (o > maxDigit)
+                      continue;
+
+                    // sum of third row must be identical to first row
+                    auto l = sum - i - j - k;
+                    if (l > maxDigit)
+                      continue;
+
+                    // sum of fourth row must be identical to first row
+                    auto p = sum - m - n - o;
+                    if (p > maxDigit)
+                      continue;
+
+                    // check diagonal, too
+                    if (sum != a + f + k + p)
+                      continue;
+
+                    // yes, found a solution
+                    result++;
+                    // mirror grid along diagonal, too
+                    if (b < e)
+                      result++;
+                  }
+                }
+              }
+        }
+
+  // add "inverted" solutions
+  if (even)
+    result *= 2;
+
+  std::cout << result << std::endl;
+  return 0;
+}