diff --git a/day3/p1.c b/day3/p1.c
index 8823abc..f0aaa6a 100644
--- a/day3/p1.c
+++ b/day3/p1.c
@@ -4,7 +4,8 @@
 #include <string.h>
 #include <stdint.h>
 #include <stdbool.h>
-#include <ctype.h>
+
+#define ISDIGIT(c) (c >= 0x30 && c <= 0x39)
 
 int main(int argc, char **argv) {
     FILE *input;
@@ -44,22 +45,22 @@ int main(int argc, char **argv) {
 
     for (ssize_t i = engine_lines-1; i >= 0; --i) {
         for (ssize_t j = engine_line_size-1; j >= 0; --j) {
-            if (isdigit(engine[i][j])) {
+            if (ISDIGIT(engine[i][j])) {
                 n += (engine[i][j]&0xf) * multiplier;
                 multiplier *= 10;
 
-                if (adjacent == false && ((j+1 <= engine_line_size-1 && !isdigit(engine[i][j+1]) && engine[i][j+1] != '.') ||
-                    (j-1 >=0 && !isdigit(engine[i][j-1]) && engine[i][j-1] != '.') ||
-                    (i+1 <= engine_lines-1 && !isdigit(engine[i+1][j]) && engine[i+1][j] != '.') ||
-                    (i-1 >= 0 && !isdigit(engine[i-1][j]) && engine[i-1][j] != '.') ||
-                    ((i+1 <= engine_lines-1 && j+1 <= engine_line_size-1) && !isdigit(engine[i+1][j+1]) && engine[i+1][j+1] != '.') ||
-                    ((i+1 <= engine_lines-1 && j-1 >= 0) && !isdigit(engine[i+1][j-1]) && engine[i+1][j-1] != '.') ||
-                    ((i-1 >= 0 && j+1 <= engine_line_size-1) && !isdigit(engine[i-1][j+1]) && engine[i-1][j+1] != '.') ||
-                    ((i-1 >= 0 && j-1 >= 0) && !isdigit(engine[i-1][j-1]) && engine[i-1][j-1] != '.'))) {
+                if (adjacent == false && ((j+1 <= engine_line_size-1 && !ISDIGIT(engine[i][j+1]) && engine[i][j+1] != '.') ||
+                    (j-1 >=0 && !ISDIGIT(engine[i][j-1]) && engine[i][j-1] != '.') ||
+                    (i+1 <= engine_lines-1 && !ISDIGIT(engine[i+1][j]) && engine[i+1][j] != '.') ||
+                    (i-1 >= 0 && !ISDIGIT(engine[i-1][j]) && engine[i-1][j] != '.') ||
+                    ((i+1 <= engine_lines-1 && j+1 <= engine_line_size-1) && !ISDIGIT(engine[i+1][j+1]) && engine[i+1][j+1] != '.') ||
+                    ((i+1 <= engine_lines-1 && j-1 >= 0) && !ISDIGIT(engine[i+1][j-1]) && engine[i+1][j-1] != '.') ||
+                    ((i-1 >= 0 && j+1 <= engine_line_size-1) && !ISDIGIT(engine[i-1][j+1]) && engine[i-1][j+1] != '.') ||
+                    ((i-1 >= 0 && j-1 >= 0) && !ISDIGIT(engine[i-1][j-1]) && engine[i-1][j-1] != '.'))) {
                     adjacent = true;
                 }
             }
-            if ((!isdigit(engine[i][j]) || j == 0) && n != 0) {
+            if ((!ISDIGIT(engine[i][j]) || j == 0) && n != 0) {
                 if (adjacent)
                     part_number += n;
                 n = 0;