As suggested by Cattledog, using a global boolean variable with the while question in the loop instead of setup seems to be a perfect solution to my problem. It works perfectly.
The end of the code is a bit different to allow fourth button switching off all LED and tell loop to ask for player Numbers again (it's just for the test code).
Now can go on with my project thanks to Cattledog and to all of you're suggestions.
Thank you all for you help solving my problem.
int playersNumber;
int askForPlayers;
void setup() {
Serial.begin(9600);
pinMode(2, INPUT_PULLUP);
pinMode(3, INPUT_PULLUP);
pinMode(4, INPUT_PULLUP);
pinMode(5, INPUT_PULLUP);
pinMode(8, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
pinMode(11, OUTPUT);
playersNumber = 0;
askForPlayers == false;
}
void loop() {
while (askForPlayers == false)
{
if (digitalRead(2) ==LOW)
{
askForPlayers = true;
playersNumber = 1;
digitalWrite(8, HIGH);
}
if (digitalRead(3) ==LOW )
{
askForPlayers = true;
playersNumber = 2;
digitalWrite(9, HIGH);
}
if (digitalRead(4) ==LOW)
{
askForPlayers = true;
playersNumber = 3;
digitalWrite(10, HIGH);
}
}
if (digitalRead(5) ==LOW)
{
askForPlayers = false;
digitalWrite(11, HIGH);
delay (1000);
digitalWrite(8, LOW);
digitalWrite(9, LOW);
digitalWrite(10, LOW);
digitalWrite(11, LOW);
}
}