#include "stm32f4xx.h"


__attribute__((optimize("O0")))
void delay(volatile int cnt) {
    while(cnt--);
}

int main(void) {
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOCEN;
    GPIOC->MODER |= (1U << (13 * 2));

    while (1) {
        GPIOC->ODR ^= (1U << 13);
        delay(500000);
    }
}