>>31 fizzbuzzだな。
#include <stdio.h>

static int sqr(int n) { return n * n; }
static int div(int n) { return n / 2; }

int main(void)
{
&nbsp; int n, t;
&nbsp; scanf("%d", &n);
&nbsp; t = n;
&nbsp; if (n % 2 == 0)
&nbsp; &nbsp; n = div(n);
&nbsp; if (n % 3 == 0)
&nbsp; &nbsp; n = sqr(n);
&nbsp; if (t == n)
&nbsp; &nbsp; n = sqr(n) - t;
&nbsp; printf("%d\n", n);
&nbsp; return 0;
}