labafile

#include <stdio.h>
#include <string.h>
#include <conio.h>
#include <stdlib.h>
int main()
{
    int k = 0;
    FILE* F;
    char str[100];
    char FILEName1[20];
    char FILEName2[20];
    puts("Enter first file name");
    gets_s(FILEName1, 20);
    fopen_s(&F, FILEName1, "w+b");
    puts("Enter strings");

    while (gets_s(str, 100), strlen(str) != 0)
    {
        fputs(str,F);
        fputs("\n", F);
    }
    rewind(F);
    puts("FileF");
    while (fgets(str, 100, F) > 0)
    {
        puts(str);

    }
    rewind(F);
    FILE* G;
    puts("Enter second file name");
    gets_s(FILEName2, 20);
    fopen_s(&G, FILEName2, "w+b");
    while (fgets(str, 100, F) > 0)
    {
        if (k % 2 == 0)
        {
            fputs(str, G);
        }
        k++;
    }
    fclose(F); fclose(G);
    puts("Elements of file G");
    fopen_s(&G, FILEName2, "r+b");
    int num = 1;
    while (fgets(str, 100, G) > 0)
    {
        printf_s("string order %d     ", num);
        puts(str);
        num += 2;
    }
    fclose(G);
    return(0);
}