void insertion_sort (int *a, int n) {
  for (int i = 1; i < n; ++i){
    int min_i = 0;
    if (a[i] < a[i-1]){
      for (int j = 0; j < i; ++j){
          if (a[j] > a[i]){
            min_i = j;
            break;
          }
      }
      int temp = a[i];
      for (int k = i; k > min_i; --k){
        a[k]=a[k-1];
      }
      a[min_i]=temp;
    }
  }
}