STM32F030 IDR Register reads incorrect value

Hi.

I struggle with stm32f030r8 arm programming on atollic true studio ide.

I have some problem with reading correct data from idr register.

I make pull down PUPR register of GPIOB(0,1,2,3).

Other pins of GPIOB is output that i make with MODER register.

when i read idr data under loop every time i read F value but there is not any input.

Please help me to solve this problem 

It takes my 25 days from my life.))

#include "main.h"

int main(void)
{
volatile static uint16_t PortDataInput=0x00;
RCC->CR|=(uint32_t)0xF1; //set hsi clock source and with max speed
GPIOB->PUPDR|=0xAA; //set firt 4 bit of portb as pull down
GPIOB_RCC->AHBENR|=(1<<18); //enable portb clock source
GPIOB->MODER|=0x55555500; //set firt 4 bit of portb as input
GPIOB->OTYPER|=0x00000000; //set output pins of portb as push pull
while (1)
{
PortDataInput=GPIOB->IDR;
PortDataInput&=0xF;

}