// String application_command = "{10;12; 4;5; 2}";
// String application_command = "10;12; 4;5; 2";

String application_command = "ST=10:12:0";

String getValue(String data, char separator, int index) 
{ 
  int found = 0; 
  int strIndex[] = {0, -1}; 
  int maxIndex = data.length()-1; 
 
  for(int i=0; i<=maxIndex && found<=index; i++){ 
    if(data.charAt(i)==separator || i==maxIndex){ 
        found++; 
        strIndex[0] = strIndex[1]+1; 
        strIndex[1] = (i == maxIndex) ? i+1 : i; 
    } 
  } 
 
  return found>index ? data.substring(strIndex[0], strIndex[1]) : ""; 
} 

void setup() {
  Serial.begin(9600);
  String firstPart = getValue(application_command,':',0); 
  Serial.println(firstPart);
 

}

void loop() {
  // put your main code here, to run repeatedly:

}


// String cmd = "r3=+639309096290";

// void setup(){

//   Serial.begin(9600);

//   Serial.println(cmd.indexOf("r3=") > -1 );
// }

// void loop(){

// }