String input;
int loop_mx;
int loop_nbr;
 unsigned long previoust=0;
  unsigned long  time_now=0;
   unsigned long diff=0;
    char incomingByte ;
    void(* resetFunc) (void) = 0;
     
     void setup() {
       Serial.begin (9600);
       Serial.println("holà , dis moi" );
       }

       void getnbr() {  
        if (Serial.available()) {
        input="";
            delay(20); 
                while(Serial.available()) 
                    { incomingByte  = Serial.read();
                          input.concat(incomingByte);
                              }
                                  input.toUpperCase ();
                                      Serial.println(input); 
                                           String dist2;
                                                 if (input.indexOf("C") > 0) {
                                                       int pp= input.indexOf("C");
                                                           
                                                             for( uint8_t j=pp+1;j<pp+4;j++)   
                                                               {if(isDigit(input.charAt(j))) 
                                                                 {dist2+=input.charAt(j);  } 
                                                                      }
                                                                       
                                                                         int rtt=dist2.toInt();
                                                                         Serial.println (String(rtt));
                                                                          loop_mx=rtt;
                                                                                }
                                                                                  }
                                                                                    }
                                                                                    void loop() {  
                                                                                     getnbr();
                                                                                       if (loop_mx >0) {
                                                                                        time_now= millis();
                                                                                         diff=time_now-previoust;
                                                                                           if (diff >=1000) {
                                                                                               loop_mx--;
                                                                                               Serial.println(loop_mx); 
                                                                                                   previoust=time_now;
                                                                                                      }    
                                                                                                         if (loop_mx ==0) {
                                                                                                          Serial.println("fini"); 
                                                                                                        //  resetFunc();
                                                                                                         }
                                                                                                           }
                                                                                                           }