volatile bool switch_1=false;
void setup() {
  // put your setup code here, to run once:
DDRF|=0xFF;
DDRK|=0x00;
PORTK|=0x00;
}

void loop() {
  // put your main code here, to run repeatedly:
while(1){
  if(PINK&(1<<PK0)){
    switch_1=true;
  }
  if(switch_1){
    PORTF^=0xFF;
    delay(500);
  }
}
}