#include <iostream>
#include <fstream>
#include <string>
#define _Z 'z'
#define _A 'a'

using namespace std;

string input;
int shift;
int length;

void codeString(){
   for (int i = 0; i < length; i++){
        if (isalpha(input[i])){
           input[i] = tolower(input[i]);
           for (int j = 0; j < shift; j++){
               if (input[i] == _Z){
                  input[i] = _A;
               }
               else
               input[i]++;
           }
        }
    }
}

void printString(){
    cout << "\nResult:  " << input << endl;
}

void getString (){
    char* doc = new char;
    cout << "Enter FILENAME: ";
    cin >> doc;
    ifstream str(doc);
    if (str.fail()){
       cout << "Can't open file: " << doc << endl;
       system("pause");
       exit(1);
    }
    delete doc;
    while (getline(str, input));
    length = (int)input.length();
}

int main(){
    getString();

    cout << "Enter SHIFT: ";
    cin >> shift;

    codeString();
    printString();

    system("pause");
    return 0;
}