diff --git a/numbers/hexen.c b/numbers/hexen.c
new file mode 100644
index 0000000..9fdbd13
--- /dev/null
+++ b/numbers/hexen.c
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#define MAXLEN 4000001
+
+int main() {
+	char x;
+	char* res = (char*)calloc(MAXLEN, sizeof(char));
+	
+	char buf[5] = "";
+	int i, len;
+
+	len = 0;
+
+	while (((x = getchar()) != '\n' ) && (x != EOF)) {
+		switch (x) {
+			case '0':
+				strcpy(buf, "0000");
+				break;
+			case '1':
+				strcpy(buf, "0001");
+				break;
+			case '2':
+				strcpy(buf, "0010");
+				break;
+			case '3':
+				strcpy(buf, "0011");
+				break;
+			case '4':
+				strcpy(buf, "0100");
+				break;
+			case '5':
+				strcpy(buf, "0101");
+				break;
+			case '6':
+				strcpy(buf, "0110");
+				break;
+			case '7':
+				strcpy(buf, "0111");
+				break;
+			case '8':
+				strcpy(buf, "1000");
+				break;
+			case '9':
+				strcpy(buf, "1001");
+				break;
+			case 'A':
+				strcpy(buf, "1010");
+				break;
+			case 'B':
+				strcpy(buf, "1011");
+				break;
+			case 'C':
+				strcpy(buf, "1100");
+				break;
+			case 'D':
+				strcpy(buf, "1101");
+				break;
+			case 'E':
+				strcpy(buf, "1110");
+				break;
+			case 'F':
+				strcpy(buf, "1111");
+				break;
+		}
+
+		for (i = 0; i < 4; ++i) {
+			res[len++] = buf[i];
+		}
+	}
+	
+	for (i = 0; res[i] == '0'; ++i);
+	if (i == len) {
+		printf("0\n");
+		free(res);
+		return 0;
+	}
+	printf("%s\n", res+i);
+	free(res);
+	return 0;
+}