Program to Find the nth term of the series

Find the Nth term in a mixed geometric series where odd positions follow powers of 2 and even positions follow powers of 3.

Understand the Problem

Problem Statement

This series is a mixture of 2 series - all the odd terms in this series form a geometric series (powers of 2) and all the even terms form another geometric series (powers of 3). Write a program to find the Nth term in the series.

The value N in a positive integer that should be read from STDIN. The Nth term that is calculated by the program should be written to STDOUT. Other than value of n th term, no other character / string or message should be written to STDOUT.

For example, if N=16, the 16th term in the series is 2187, so only value 2187 should be printed to STDOUT.

You can assume that N will not exceed 30.

Constraints

N is a positive integer
1 ≤ N ≤ 30
Input must be read from standard input
Output must be written to standard output
Only the numeric result should be printed

Examples

Example 1

Input

Output

Explanation

Position 16 is even, so we calculate 3^(16/2 - 1) = 3^7 = 2187

Example 2

Input

Output

Explanation

Position 13 is odd, so we calculate 2^(13/2) = 2^6 = 64

Solution

#include <stdio.h>
#include <math.h>

int main() {
    int n;
    scanf("%d", &n);
    
    if (n % 2 == 0) {
        // Even position: power of 3
        int power = n / 2 - 1;
        printf("%d", (int)pow(3, power));
    } else {
        // Odd position: power of 2
        int power = n / 2;
        printf("%d", (int)pow(2, power));
    }
    
    return 0;
}

Time:O(1)

Space:O(1)

Approach:

1. Read integer N from standard input

2. Check if N is even or odd using modulo operator

3. For even positions: calculate 3^(N/2 - 1) using pow() function

4. For odd positions: calculate 2^(N/2) using pow() function

5. Print the result using printf()

6. Return 0 to indicate successful execution

Visual Explanation

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