とりあえず一部C++の恩恵を受けつつswitch文も使って、あ、ifは使ってないや
#include <iostream>
#include <numeric>
using namespace std;
int date2days(int month, int day)
{
  static char days[] = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30 };
  return accumulate(days, days + month, day); // numeric
}
enum Day { SUN,MON,TUE,WED,THU,FRI,SAT };
ostream& operator<<(ostream& os, Day d) {
  switch (d) {
  case SUN: return os << "sun.";
  case MON: return os << "mon.";
  case TUE: return os << "tue.";
  case WED: return os << "wed.";
  case THU: return os << "thu.";
  case FRI: return os << "fri.";
  case SAT: return os << "sat.";
  default: return os;
  }
}
Day get_day(int days) { return Day((days + 5) % 7); }

int main()
{
  int   month, date;
  cin >> month >> date;
  int   days(date2days(month, date));
  Day   day(get_day(days));
  cout << days << ", " << day << endl;
}