680 Садовник-художник - Динамика

#include <stdio.h>

int main( )
{
    FILE *in = fopen("input.txt", "rt");
    FILE *out = fopen("output.txt", "wt");

    if (in && out)
    {
        int n;
        unsigned long long count = 1;
        fscanf(in, "%d", &n);

        for (int i = 0; i < n - 1; ++i)
        {
            count *= 2;
        }
        count *= 3;

        fprintf(out, "%llu\n", count);
    }
    return 0;
}