zoj 3191 Strange Clock

#include<stdio.h>#include<string.h>int main(){int a;while(1){scanf("%d",&a);if(a == -1)break;a = 360 - a;a += 90;a %= 360;if(a % 30 == 0)printf("Exactly %d o'clockn",a / 30);else{int l = a / 30;int r = l + 1;if(r == 12)r = 0;printf("Between %d o'clock and %d o'clockn",l,r);}}return 0;}