int i;

void segwrite(int n);

void loop() {
  if (digitalRead( 9)) { i--; goto nextstep; }
  if (digitalRead(10)) { i++; goto nextstep; }
  return;
  nextstep:
    if (i < 0) i = 0;
    if (i > 9) i = 9;
    analogWrite(A0, i*25);
    segwrite(i);
    delay(500);
}

void setup() {
  i = 0;
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(A0, OUTPUT);
  segwrite(i);
}

void segwrite(int n) {
  switch (n) {
    case 0:
      digitalWrite(2, LOW);
      digitalWrite(3, HIGH);
      digitalWrite(4, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(8, HIGH);
      break;
    case 1:
      digitalWrite(2, LOW);
      digitalWrite(3, LOW);
      digitalWrite(4, LOW);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, LOW);
      digitalWrite(8, LOW);
      break;
    case 2:
      digitalWrite(2, HIGH);
      digitalWrite(3, LOW);
      digitalWrite(4, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(6, LOW);
      digitalWrite(7, HIGH);
      digitalWrite(8, HIGH);
      break;
    case 3:
      digitalWrite(2, HIGH);
      digitalWrite(3, LOW);
      digitalWrite(4, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(8, LOW);
      break;
    case 4:
      digitalWrite(2, HIGH);
      digitalWrite(3, HIGH);
      digitalWrite(4, LOW);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, LOW);
      digitalWrite(8, LOW);
      break;
    case 5:
      digitalWrite(2, HIGH);
      digitalWrite(3, HIGH);
      digitalWrite(4, HIGH);
      digitalWrite(5, LOW);
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(8, LOW);
      break;
    case 6:
      digitalWrite(2, HIGH);
      digitalWrite(3, HIGH);
      digitalWrite(4, HIGH);
      digitalWrite(5, LOW);
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(8, HIGH);
      break;
    case 7:
      digitalWrite(2, LOW);
      digitalWrite(3, LOW);
      digitalWrite(4, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, LOW);
      digitalWrite(8, LOW);
      break;
    case 8:
      digitalWrite(2, HIGH);
      digitalWrite(3, HIGH);
      digitalWrite(4, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(8, HIGH);
      break;
    case 9:
      digitalWrite(2, HIGH);
      digitalWrite(3, HIGH);
      digitalWrite(4, HIGH);
      digitalWrite(5, HIGH);
      digitalWrite(6, HIGH);
      digitalWrite(7, HIGH);
      digitalWrite(8, LOW);
      break;
  }
}