int n=0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, Primer ejercicio!");
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
  if(Serial.available() !=0) {
    n = Serial.read();
    if(n>'0' && n!='1' && n<='9'){
      if(n % 2 != 0){
        while(int i=0; i=n; i++){
          while(int j=0; j=n; j++){
            if(i==0 || i==n-1){
              Serial.write('*');
            }
            else{
              if(j==0 || j==n-1){
              Serial.write('*');
              }
            }
          }
          Serial.println('\n');
          Serial.println('\r');
        }
      }
    }
  }
}