Obstacle avoiding car using l293d motor driver shield

1#include <AFMotor.h>
2
3const int trigPin = A0;
4const int echoPin  = A2;
5long duration;
6int distance;
7
8AF_DCMotor motor1(1, MOTOR12_1KHZ);
9AF_DCMotor  motor2(2, MOTOR12_1KHZ);
10AF_DCMotor motor3(3, MOTOR12_1KHZ);
11AF_DCMotor motor4(4,  MOTOR12_1KHZ);
12
13 
14
15void setup() {
16  pinMode(trigPin, OUTPUT); 
17  pinMode(echoPin, INPUT);
18
19  Serial.begin(9600);
20  
21  motor1.setSpeed(250);
22  motor2.setSpeed(250);
23  motor3.setSpeed(250);
24  motor4.setSpeed(250);
25  
26}
27
28void loop() 
29{
30  
31digitalWrite(trigPin, LOW);
32delayMicroseconds(2);
33digitalWrite(trigPin,  HIGH);
34delayMicroseconds(10);
35digitalWrite(trigPin, LOW);
36duration = pulseIn(echoPin,  HIGH);
37distance= duration*0.034/2;
38Serial.print("Distance: ");
39Serial.println(distance);
40
41movestop();
42delay(1000);
43
44if(distance  < 75)
45{   
46 
47 backward();
48    delay(1000);
49  
50     
51    movestop();
52    delay(1000);
53    
54    lookright();
55    delay(750);
56}
57else
58{
59  forward();
60  delay(1000); 
61
62}
63
64
65}
66
67
68void movestop()
69{
70  motor1.run(RELEASE);
71  motor2.run(RELEASE);
72  motor3.run(RELEASE);
73  motor4.run(RELEASE);
74}
75
76void  forward()
77{
78  motor1.run(FORWARD);
79  motor2.run(FORWARD);
80  motor3.run(FORWARD);
81  motor4.run(FORWARD);
82  motor1.setSpeed(200);
83  motor2.setSpeed(200);
84  motor3.setSpeed(200);
85  motor4.setSpeed(200);
86 
87}
88
89void backward()
90{
91  motor1.run(BACKWARD);
92  motor2.run(BACKWARD);
93  motor3.run(BACKWARD);
94  motor4.run(BACKWARD);
95  motor1.setSpeed(200);
96  motor2.setSpeed(200);
97  motor3.setSpeed(200);
98  motor4.setSpeed(200);
99 
100}
101    
102void  lookright()
103{
104  motor1.run(FORWARD);
105  motor2.run(FORWARD);
106  motor3.run(BACKWARD);
107  motor4.run(BACKWARD);
108  motor1.setSpeed(200);
109  motor2.setSpeed(200);
110  motor3.setSpeed(200);
111  motor4.setSpeed(200);
112 
113}
114
115void lookleft()
116{
117  motor1.run(BACKWARD);
118  motor2.run(BACKWARD);
119  motor3.run(FORWARD);
120  motor4.run(FORWARD);
121  motor1.setSpeed(200);
122  motor2.setSpeed(200);
123  motor3.setSpeed(200);
124  motor4.setSpeed(200);
125 
126}
127