C :

#include <stdio.h>
#include <stdlib.h>

int main()
{
	int n;
	scanf("%d", &n);
	int a[1000] = {0};
	int i=0, j=0, m;
	for (i=0; i<n; i++)
		a[i] = i+1;
	i=0;
	for (m=0; m<n; m++)
	{
		j=0;
		while (j<3)
		{
			while (a[i] == 0)
				i = (i+1) % n;
			if (j==2&&m!=n-1)
			{
				a[i]=0;
			}
			i = ((i+1) % n);
			j++;
		}
	}
	i = i-1;
	if (i<0)
		i=n-1;
	printf("%d\n", a[i]);
	return 0;
}

C++ :

#include <stdio.h>
int main() {
	int n, i, cur;
	int next[1000];
	scanf("%d", &n);
	for (i = 0;i < n;i++)
		next[i] = (i + 1) % n;
	cur = 0;
	for (i = 0;i < n - 1;i++) {
		cur = next[cur];
		next[cur] = next[next[cur]];
		cur = next[cur];
	}
	printf("%d\n", cur + 1);
	return 0;
}