Problems
Honeycomb
Honeycomb
The bee can go in honeycomb as shown in the figure — with moves 1 and 2 from upper row and with move 3 from the lower.
Input data
The number of hexagons n~(1 \le n \le 45) in the upper row. The lower row contains 1 hexagon less.
Output data
Print the number of ways to get from the first cell of the top row to the last cell of the same row.
Examples
Input example #1
1
Output example #1
1
Input example #3
3
Output example #3
2