// Online C compiler to run C program online
#include <stdio.h>

int isalnum(int c)
{
    char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890., "
                      "abcdefghijklmnopqrstuvwxyz1234567890., ";
    char *letter = alphabet;

    while(*letter != '\0' && *letter != c)
        ++letter;

    if (*letter)
        return 1;

    return 0;
}

int main() {
    char source[] = "This is an example.@#@#%$@@#%$#^)#(%*@*%$(#)(#($)#";
    char source_filtered[64];
    
    for (int i = 0; i < strlen(source_filtered); i++)
    {

     source_filtered[i] = "\0";

    }
    
    for (int i = 0; source[i] != 0; i++)
    {

        if (isalnum(source[i]))
        {
            //  printf("TRUE\n");
            source_filtered[i] = source[i];
        }

    }         
    printf(source_filtered);
    
    
    return 0;
}