Task
Time limit:
1000 ms,
Memory limit:
256 Mb
For a given positive integer n≥2, calculate the sum 1 × 2 + 2 × 3 + ... + (n-1) × n. Output the answer in the form of a calculated expression and its value exactly as shown in the example.
Input: A natural number is entered.
Output: Output the answer to the problem.
Example
| № |
Input |
Output |
| 1 |
4 |
1*2+2*3+3*4=20 |