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dt = P - y^2

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DEFDBL A-Z:
DEF SEG = 0: SCREEN 12
CLEAR , , 2000
CLS

INPUT ; "Bitte P eingeben"; P
IF P = 0 OR P = 1 THEN END
y = (P - 1) / 2
s = y

start:
dt = P - y^2
t = y
IF dt < 0 OR dt = 0 THEN y = y - INT(s / 2): GOTO sp
IF dt > 0 THEN y = y + INT(s / 2)

sp:
s = INT(s / 2)
IF y = t THEN GOTO weiter
GOTO start

weiter:
tt = tt + 1
y = y + 1
dt = P - y^2
IF dt < 0 or dt=0 THEN GOTO runter
IF dt > 0 THEN GOTO weiter

schluss:
CLS
d = SQR(ABS(dt)) * 2
ga = INT(((d / 2 - 1) ^ 2) / 2)
LOCATE zz + 1, 1: PRINT P; " = "; (y-d/2); " * "; (y+d/2); ", ga = "; ga;
END

runter:
IF tt > 5 THEN GOTO schluss
tt = tt + 1
y = y - 1
dt = P - y^2

IF dt < 0 or dt=0 THEN GOTO runter
IF dt > 0 THEN GOTO weiter