C program read 20 number from user and find maximum minimum, sum, average

#include
int main()
{
 int number[30];
 int i, j, a,large,small,avg,sum=0;
 printf("Enter the numbers \n");
 for (i = 0; i < 20; ++i)
 scanf("%d", &number[i]);
 for (i = 0; i < 20; ++i)
 {
 for (j = i + 1; j <20; ++j)
 {
 if (number[i] < number[j])
 {
 a = number[i];
 number[i] = number[j];
 number[j] = a;
 }
 }
 }
 printf("The numbers arranged in descending order are given below \n");
 for (i = 0; i < 20; ++i)
 {
 printf("%d\n", number[i]);
 }
 printf("The 2nd largest number is = %d\n", number[1]);
 printf("The 2nd smallest number is = %d\n", number[20 - 2]);
 large=small=number[0];
 for(i=1; i<20; ++i)
 {
 if(number[i]>large)
 large=number[i];
 if(number[i]