Serial.read control LED flashing with letters ('f' and 's')

int LEDpin = 7;
int lapse = 0;
int inputChar;
int inputNumber;

void setup() {
  Serial.begin(9600);
}


void loop() {
  lapse=0;
  pinMode(LEDpin, OUTPUT);
  if (Serial.available()>0){
    delay(5);
    while (Serial.available()>0){
      inputChar = Serial.read();
    }
    if (inputChar == 'f'){
      lapse = 100;
      while (lapse > 0){
       digitalWrite(LEDpin,HIGH);
       delay(lapse);
       digitalWrite(LEDpin,LOW);
       delay(lapse);
       lapse = lapse -5;
      }
    }
     else if (inputChar == 's'){
       lapse = 0;
       while (lapse < 2000){
       digitalWrite(LEDpin,HIGH);
       delay(lapse);
       digitalWrite(LEDpin,LOW);
       delay(lapse);
       lapse = lapse+100;
      }
     }
    }
 }