Index: aoc2024.c
==================================================================
--- aoc2024.c
+++ aoc2024.c
@@ -36,10 +36,24 @@
     if (masat(data, size, row, col, +1, -1)) finds++;
     if (masat(data, size, row, col, +1,  0)) finds++;
     if (masat(data, size, row, col, +1, +1)) finds++;
     return finds;
 }
+
+static bool Xmasat(char *data, unsigned size, unsigned row, unsigned col) {
+    unsigned tmp = 0;
+    if (data[rcmap(size, row, col)] != 'A') return false;
+    if (data[rcmap(size, row-1, col-1)] == 'M') tmp |= 1;
+    if (data[rcmap(size, row-1, col-1)] == 'S') tmp |= 2;
+    if (data[rcmap(size, row-1, col+1)] == 'M') tmp |= 4;
+    if (data[rcmap(size, row-1, col+1)] == 'S') tmp |= 8;
+    if (data[rcmap(size, row+1, col+1)] == 'M') tmp |= 1;
+    if (data[rcmap(size, row+1, col+1)] == 'S') tmp |= 2;
+    if (data[rcmap(size, row+1, col-1)] == 'M') tmp |= 4;
+    if (data[rcmap(size, row+1, col-1)] == 'S') tmp |= 8;
+    return tmp == 15;
+}
 
 void aoc202404(char *data, size_t len) {
     (void)len; // unused argument
     // assume data is well-formatted and has the same number of rows and columns
     unsigned size = strchr(data, '\n') - data;
@@ -53,17 +67,21 @@
           size, data[rcmap(size, 0, 0)], data[rcmap(size, 0, 1)],
           data[rcmap(size, 1, 0)], data[rcmap(size, 1, 1)],
           data[rcmap(size, 2, 0)], data[rcmap(size, 2, 1)]);
     printf("ends with %c%c.\n", data[rcmap(size, size-1, size-2)], data[rcmap(size, size-1, size-1)]);
     #endif
-    unsigned xmascount = 0;
+    unsigned xmascount = 0, Xmascount = 0;
     for (unsigned row = 0; row < size; row++) {
         for (unsigned col = 0; col < size; col++) {
             xmascount += xmasat(data, size, row, col);
+            if ((1 <= row) && (row < size - 1) && (1 <= col) && (col < size - 1)) {
+                Xmascount += Xmasat(data, size, row, col);
+            }
         }
     }
     printf("XMAS appears %u times in the little Elf's word search.\n", xmascount);
+    printf("X-MAS appears %u times in the little Elf's word search.\n", Xmascount);
 }
 
 void aoc202403(char *data, size_t len) {
     (void)len; // unused argument
     unsigned sumproducts = 0, sumproducts2 = 0, term[2];