10 INPUT "Enter a year: ", Y
20 X = Y
30 GOSUB 100
40 IF P = 4 THEN L = 1
50 X = Y - 1
60 GOSUB 100
70 IF P = 3 THEN L = 1
80 IF L = 1 THEN PRINT Y; " is a long year." ELSE PRINT Y;" is not a long year."
90 END
100 P = X + INT(X/4) - INT(X/100) + INT(X/400)
110 P = P MOD 7
120 RETURN