#include <iostream>
using namespace std;
int firstOcc(int arr[], int n, int key) {
  int start = 0;
  int end = n-1;
  int ans = -1;
  int mid = start + (end-start)/2;
  while (start <= end) {
    if (arr[mid] == key) {
      ans = mid;
      end = mid - 1;
    }
    else if (arr[mid] < key) {
      start = mid + 1;
    }
    else {
      end = mid - 1;
    } 
    mid = start + (end-start)/2;
  }
  return ans;
}
int lastOcc(int arr[], int n, int key) {
  int start = 0;
  int end = n-1;
  int ans = -1;
  int mid = start + (end-start)/2;
  while (start <= end) {
    if (arr[mid] == key) {
      ans = mid;
      start = mid + 1;
    }
    else if (arr[mid] < key) {
      start = mid + 1;
    }
    else {
      end = mid - 1;
    } 
    mid = start + (end-start)/2;
  }
  return ans;
}
int main() {
  int array[6] = {1,2,2,2,2,3};
  int first = firstOcc(array,6,2);
  cout << "first occurance of 2 is at index " << first << endl;
  int last = lastOcc(array,6,2);
  cout << "last occurance of 2 is at index " << last << endl;
  return 0;
}