Negative days completion.

programs/abs/main.c

@@ -0,0 +1,17 @@
+#include <stdio.h>
+
+int main(void) {
+    int x, y;
+
+    printf("Input integer: ");
+    scanf("%d", &x);
+
+    y = x;
+
+    if (y < 0)
+        y = -y;
+    
+    printf("Absolute value of %d is %d.\n", x, y);
+
+    return 0;
+}