public class MyClass {
private static int findSmallestMissingNumber(int[] arr) {
int min = arr[0];
int size = arr.length;
for (int i = 1; i < size; i++) {
if (arr[i] > min + 1) {
return min + 1;
}
else {
min = arr[i];
}
}
return -1;
}
public static void main(String args[]) {
int[] arr = {18, 19, 20, 27, 33, 36, 40, 42};
System.out.print(findSmallestMissingNumber(arr));
}
}
/*
run:
21
*/