반말을 존댓말로

#include <stdio.h>
#include <wchar.h>
#include <locale.h>
 
int findatrear(wchar_t [], wchar_t []);
void replace(wchar_t [], wchar_t []);
int getline(wchar_t [], int);
main(){
	wchar_t mainstr[1000];
	setlocale(LC_CTYPE,"kor");
 
	while (getline(mainstr, 1000) > 0)
	{
		if (findatrear(mainstr, L"이다\n"))
			replace(mainstr, L"입니다\n");	
		else if (findatrear(mainstr, L"한다\n"))
			replace(mainstr, L"합니다\n");
		else if (findatrear(mainstr, L"된다\n"))
			replace(mainstr, L"됩니다\n");
		wprintf(L"%s", mainstr);
	}	
}
 
int findatrear(wchar_t str[], wchar_t strtofind[])
{
	int i = wcslen(str);
 
	if (wcscmp(&str[i-3], strtofind) == 0)
		return 1;
	return 0;
}
 
void replace(wchar_t str[], wchar_t strtoreplace[])
{
	int i = wcslen(str);
 
	str[i-3] = L'\0';
	wcscat(str, strtoreplace);
}
 
int getline(wchar_t str[], int max)
{
	if (fgetws(str,max,stdin) == NULL)
		return 0;
	else
		return wcslen(str);
}