Объединить два бинарных файла в один

int main() {
std::ifstream inFirst( "f1.bin", std::ios::in | std::ios::binary );
std::ifstream inSecond( "f2.bin", std::ios::in | std::ios::binary );
std::ofstream outThird( "f3.bin", std::ios::out | std::ios::binary );
 
char char1;
char char2;
 
if (!( inFirst && inSecond && outThird ))
return -1;
 
inFirst.read( reinterpret_cast< char * >( &char1 ), sizeof( char1 ));
inSecond.read( reinterpret_cast< char * >( &char2 ), sizeof( char2 ));
 
while ( inFirst && inSecond ) {
if ( char1 < char2 ) {
outThird.write( reinterpret_cast < const char * >( &char1 ), sizeof( char1 ));
inFirst.read( reinterpret_cast < char * >( &char1 ), sizeof( char1 ));
} else {
outThird.write( reinterpret_cast < const char * >( &char2 ), sizeof( char2 ));
inSecond.read( reinterpret_cast < char * >( &char2 ), sizeof( char2 ));
}
}
 
while ( inFirst ) {
outThird.write( reinterpret_cast< const char * >( &char1 ), sizeof( char1 ));
inFirst.read( reinterpret_cast< char * >( &char1 ), sizeof( char1 ));
}
 
while ( inSecond ) {
outThird.write( reinterpret_cast< const char * >( &char2 ), sizeof( char2 ));
inSecond.read( reinterpret_cast< char * >( &char2 ), sizeof( char2 ));
}
 
return 0;
}

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <string>
#include <cstdio>
 
using namespace std;
 
 
int main()
{ 
    FILE *origin = NULL;
    FILE *output = NULL;
 
    char buffer[200];
 
    fopen_s(&origin,"input.txt", "r");
    
    fopen_s(&output,"output.txt", "w");
 
    const char *path = "C:\\Users\\User\\Desktop\\docs\\%d.txt";
    for (int i = 1; i < 4; i++)
    {
        sprintf_s(buffer, path, i);
        fopen_s(&origin, buffer, "r");
        if (origin == NULL) continue;
        int c = 0;
        while ((c = fgetc(origin)) != EOF)
        {
            fprintf(output, "%c", c);
        }
        fclose(origin);
    }
    fclose(output);
    return 0;