Switch case problem....

You were right about the upper exclusive, I've done that to test it

#include <LiquidCrystal.h>
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
int res =0;

long dicea;



void setup() {                

  Serial.begin(9600);
  
  lcd.begin(16, 2);
  
 
 }


void loop() {
  
  
      res = analogRead(15);
      
     
      
      if (res < 350) {
        dicea = random(1,7);
        lcd.setCursor(0, 0);
        lcd.print(dicea);
        delay(5000);
                     }
lcd.clear();

}

And I saw another problem, when I reset my program, it show the same numbers, how can I make it look like a true number generator...

thanks