C :

#include<stdio.h>

int main()
{
	int m,n;
	int a;
	while(scanf("%d",&m)!=EOF,m!=-1)
	{
		n=m/30;
		if(m%30==0)
		{
			if(n<=3)
				a=3-n;
			else
				a=3-n+12;
			printf("Exactly %d o'clock\n",a);
		}
		else
		{
			if(m<90||m>120)
			{
				if(m<90)
					a=3-n;
				else
					a=3-n+12;
				printf("Between %d o'clock and %d o'clock\n",a-1,a);
			}
			else
			{
				printf("Between 11 o'clock and 0 o'clock\n");
			}
		}
	}
	return 0;
}

C++ :

#include <stdio.h>

int main() {
	int a, x, y;
	while (scanf("%d", &a) != EOF, a != -1) {
		if (a % 360 % 30 == 0 && a % 360 / 30 <= 3) {
			x = 3 - a % 360 / 30;
			printf("Exactly %d o'clock\n", x);
		} else if (a % 360 % 30 == 0 && a % 360 / 30 > 3) {
			x = 15 - a % 360 / 30;
			printf("Exactly %d o'clock\n", x);
		} else if (a % 360 % 30 != 0 && a % 360 / 30 <= 3) {
			x = 3 - a % 360 / 30;
			if (x > 0)
				y = x - 1;
			else
				y = 11;
			printf("Between %d o'clock and %d o'clock\n", y, x);
		} else if (a % 360 % 30 != 0 && a % 360 / 30 > 3) {
			x = 15 - a % 360 / 30;
			y = x - 1;
			printf("Between %d o'clock and %d o'clock\n", y, x);
		}
	}
	return 0;
}