Не может открыть файл для чтения

if(!F2)
  {
    cout << "Error opening F2.txt" << endl;
  }

#include <fstream>
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
using std::ifstream;
 
int main()
{
  char Ch1, Ch2;
  int EntryNum = 0;
  // Ищет указанную строку в файле и выводит количество её вхождений.
  ifstream F1;
  ifstream F2;
  enum FoundEntryEnum{NoFoundEntry, IsFoundEntry};
  FoundEntryEnum FoundEntry = NoFoundEntry;
  F1.open("F1.txt");
  F2.open("F2.txt");
   
  F2.get(Ch2);
  F1.get(Ch1);
  { 
    cout << "Ch2 == " << Ch2 << endl;
    cout << "Ch1 == " << Ch1 << endl;
    
    if(Ch1 == Ch2)
    {
      if(FoundEntry == NoFoundEntry)
        FoundEntry = IsFoundEntry;
      if(F2.get(Ch2))
      {
        cout << "F2.get(Ch2)" << endl;
      }
      else
      {
        //увеличиваем число вхождений
        EntryNum++;
        cout << "EntryNum++ now. EntryNum == " << EntryNum << endl;
        //перемотка файла с подстрокой
        F2.close();
        ifstream F2;
        F2.open("F2.txt");
        if(!F2)
        {
          cout << "Error opening F2.txt" << endl;
        }
        if(F2.get(Ch2))
        {
          cout << "The first character after rewriting is Ch2 == " << Ch2 << endl;
        } 
        else
        {
          cout << "No possible to read first character after rewriting"<< endl;
        }
        FoundEntry = NoFoundEntry;
      }
    } 
  }
  
  F1.get(Ch1);
  { 
    cout << "Ch2 == " << Ch2 << endl;
    cout << "Ch1 == " << Ch1 << endl;
    
    if(Ch1 == Ch2)
    {
      if(FoundEntry == NoFoundEntry)
        FoundEntry = IsFoundEntry;
      if(F2.get(Ch2))
      {
        cout << "F2.get(Ch2)" << endl;
      }
      else
      {
        //увеличиваем число вхождений
        EntryNum++;
        cout << "EntryNum++ now. EntryNum == " << EntryNum << endl;
        //перемотка файла с подстрокой
        F2.close();
        ifstream F2;
        F2.open("F2.txt");
        if(!F2)
        {
          cout << "Error opening F2.txt" << endl;
        }
        if(F2.get(Ch2))
        {
          cout << "The first character after rewriting is Ch2 == " << Ch2 << endl;
        } 
        else
        {
          cout << "No possible to read first character after rewriting"<< endl;
        }
        FoundEntry = NoFoundEntry;
      }
    } 
  }
  
  F2.close();
  F2.open("F2.txt");
  if(!F2)
  {
    cout << "Error opening F2.txt" << endl;
  }
  
  if(F2.get(Ch2))
  {
    cout << "1The first character after rewriting is Ch2 == " << Ch2 << endl;
  } 
  else
  {
    cout << "1No possible to read first character after rewriting"<< endl;
  }
 
  
  if(F2.get(Ch2))
  {
    cout << "1The second character after rewriting is Ch2 == " << Ch2 << endl;
  } 
  else
  {
    cout << "1No possible to read second character after rewriting"<< endl;
  }
 
 
  cout << "At the end. Quantity of lines's entries == " << EntryNum << endl;
  cout << "At the end. Ch2 == " << Ch2 << endl;
  F1.close();
  F2.close();
  return 0;
}

#include <fstream>
#include <iostream>
using std::cin;
using std::cout;
using std::endl;
using std::ifstream;
using std::ofstream;
 
int main()
{
  char Ch1;
  ifstream F1;
  F1.open("F1.txt");
  if(!F1)
    cout << "Error opening F1.txt" << endl;
  if(F1.get(Ch1))
    cout << "Ch1 == " << Ch1 << endl;
  if(F1.get(Ch1))
    cout << "Ch1 == " << Ch1 << endl;
  if(F1.get(Ch1))
    cout << "Ch1 == " << Ch1 << endl;
  F1.close();
  F1.open("F1.txt");
  if(!F1)
    cout << "Error opening F1.txt" << endl;
  if(F1.get(Ch1))
    cout << "Ch1 == " << Ch1 << endl;
  if(F1.get(Ch1))
    cout << "Ch1 == " << Ch1 << endl;
  if(F1.get(Ch1))
    cout << "Ch1 == " << Ch1 << endl;
  F1.close();
  return 0;
}