public static void Main()
Console.WriteLine("teclea tu calificacion");
calif = int.Parse(Console.ReadLine());
case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8: case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: case 19: case 20: case 21: case 22: case 23: case 24: case 25: case 26: case 27: case 28: case 29: case 30: case 31: case 32: case 33: case 34: case 35: case 36: case 37: case 38: case 39: case 40: case 41: case 42: case 43: case 44: case 45: case 46: case 47: case 48: case 49: case 50: case 51: case 52: case 53: case 54: case 55: case 56: case 57: case 58: case 59:
Console.WriteLine("Tu letra es: E");
case 60: case 61: case 62: case 63: case 64: case 65: case 66: case 67: case 68: case 69:
Console.WriteLine("Tu letra es: D");
case 70: case 71: case 72: case 73: case 74: case 75: case 76: case 77: case 78: case 79:
Console.WriteLine("Tu letra es: C");
case 80: case 81: case 82: case 83: case 84: case 85: case 86: case 87: case 88: case 89:
Console.WriteLine("Tu letra es: B");
Console.WriteLine("Tu letra es: A");