c program for shell sort

#include <stdio.h>
#include <stdbool.h>
#define MAX 7
int intArray[MAX] = {4,6,3,2,1,9,7};
void printline(int count){
int i;
for(i = 0;i <count-1;i++){
printf("=");
}
printf("=\n");
}
void display(){
int i;
printf("[");
// navigate through all items
for(i = 0;i<MAX;i++){
printf("%d ",intArray[i]);
}
printf("]\n");
}
void shellSort(){
int inner, outer;
int valueToInsert;
int interval = 1;
int elements = MAX;
int i = 0;
while(interval <= elements/3) {
interval = interval*3 +1;
}
while(interval > 0) {
printf("iteration %d#:",i);
display();
for(outer = interval; outer < elements; outer++) {
valueToInsert = intArray[outer];
inner = outer;
while(inner > interval -1 && intArray[inner - interval]
>= valueToInsert) {
intArray[inner] = intArray[inner - interval];
inner -=interval;
printf(" item moved :%d\n",intArray[inner]);
}
intArray[inner] = valueToInsert;
printf(" item inserted :%d, at position :%d\n",valueToInsert,inner);
}
interval = (interval -1) /3;
i++;
}
}
int main() {
printf("Input Array: ");
display();
printline(50);
shellSort();
printf("Output Array: ");
display();
printline(50);
return 1;
}