Compute n! = 1 × 2 × … × n (with 0! = 1).
Input
A single integer n.
Output
The value of n!. (It gets large — pick a language with big integers, or keep within 64-bit for the given limits.)
Factorial
Easymath
Examples
Example 1
- Input
5
- Output
120
1·2·3·4·5 = 120.
Example 2
- Input
0
- Output
1
0! = 1.
Example 3
- Input
10
- Output
3628800
10! = 3628800.
Constraints
- 0 <= n <= 20
Hints
Reveal hint 1
Multiply the numbers from 1 up to n.
Reveal hint 2
0! is defined as 1 — the empty product.
Reference solution (spoiler — try it yourself first)
Approach
Multiply 1 through n; start the running product at 1 so that n = 0 yields 1.
n = int(input())
f = 1
for i in range(2, n + 1):
f *= i
print(f)
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