sum34
Given n, you have to find out the sum of the digits of the number of numbers with length n which are formed using only digits 3 and 4.
Example
- For
n = 4, the output should besum34(n) = 7.
Desired numbers with length4are:3333, 3334, 3343, 3433, 4333, 3344, 3434, 4334, 4343, 4433, 3443, 3444, 4344, 4434, 4443, 4444. So, there are16desired numbers, and the answer is1 + 6 = 7.
Input/Output:
-
[execution time limit] 2 seconds
-
[input] integer n
Guaranteed constraints:
1 ≤ n ≤ 5 · 104. -
[output] integer
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