#include<stdio.h>

typedef enum {MON, TUE, WED, THU, FRI, SAT, SUN} DayType;

DayType nextDay(DayType day) {
  return (day+1) % 7;
}

DayType prevDay(DayType day) {
  return (day+6) % 7;
}

void printDay(DayType day) {
  switch(day) {
  case MON: printf("monday\n"); break;
  case TUE: printf("tuesday\n"); break;
  case WED: printf("wednesday\n"); break;
  case THU: printf("thursday\n"); break;
  case FRI: printf("friday\n"); break;
  case SAT: printf("saturday\n"); break;
  case SUN: printf("sunday\n"); break;
  }
}

int main() {
  DayType day;
  day = FRI;
  printDay(day);

  printDay(prevDay(MON));
  printDay(nextDay(SUN));

}