character stuffing

#include <stdio.h>
#include <string.h>

void main() {
    int i = 0, j = 0, n, pos;
    char a[20], b[50], ch;
    printf("Enter string\n");
    scanf("%s", a); 
    n = strlen(a);
    printf("Enter position\n");
    scanf("%d", &pos); 
    while (pos > n) {
        printf("Invalid position, Enter again: ");
        scanf("%d", &pos);
    }
    printf("Enter the character\n");
    getchar(); 
    ch = getchar(); 

    // Initialize the stuffed string with "dlestx"
    b[0] = 'd';
    b[1] = 'l';
    b[2] = 'e';
    b[3] = 's';
    b[4] = 't';
    b[5] = 'x';
    j = 6;
    while (i < n) {
        // Insert "dle" + character + "dle" at the specified position
        if (i == pos - 1) {
            b[j] = 'd';
            b[j + 1] = 'l';
            b[j + 2] = 'e';
            b[j + 3] = ch;
            b[j + 4] = 'd';
            b[j + 5] = 'l';
            b[j + 6] = 'e';
            j = j + 7;
        }
        if (a[i] == 'd' && a[i + 1] == 'l' && a[i + 2] == 'e') {
            b[j] = 'd';
            b[j + 1] = 'l';
            b[j + 2] = 'e';
            b[j + 3] = 'd';
            b[j + 4] = 'l';
            b[j + 5] = 'e';
            j = j + 6;
            i = i + 3; 
        } else {
            b[j] = a[i];
            j++;
            i++;
        }
    }
    b[j] = 'd';
    b[j + 1] = 'l';
    b[j + 2] = 'e';
    b[j + 3] = 'e';
    b[j + 4] = 't';
    b[j + 5] = 'x';
    b[j + 6] = '\0'; 

    printf("Stuffed string is:\n%s\n", b);
}