cipher problems help please due in 30 minutes

[ckking]

ok the part that i had earlier was supposed to part of this cipher, im having trouble with it not converting spaces

    char ch;
    char inputfile[81];
    cout << "enter input filename:"<<endl;
    cin.getline(inputfile, 81);
    char outputfile[81];
    cout << "enter output filename:"<<endl;
    cin.getline(outputfile, 81);
    string keyword;
    cout << "enter keyword:" << endl;
    getline(cin, keyword);
    ifstream infile;
     ofstream oufile;
     infile.open (inputfile);
     oufile.open (outputfile);
    if (!outputfile)
     {
         cout << "ERROR: CANNOT OPEN output file FILE\n";
         return 5;
     }
    else if (!inputfile)
     {
         cout << "ERROR: CANNOT OPEN input file FILE\n";
         return 6;
     }
 
 
    int answer = menu();
 
 
    if ( answer == 1)
    {
>>        for(int i=0; infile >> ch  ; i = (i+1)% keyword.length())
        {
            ch =ch+keyword[i];
            oufile << ch;
        }
    }
    else if ( answer == 2)
    {
>>        for(int i=0; infile >> ch ; i = (i+1)% keyword.length())
        {
            ch =ch-keyword[i];
            oufile << ch;
        }
    }
    infile.close ();
    oufile.close ();
 
    return 0;
}
int menu ()
{
    int r;
    do 
    {    cout << "for encryption enter 1, for decryption enter 2, and to quit "; 
        cout <<    "enter 3"<< endl;
        cin >> r;
    }    while ( r != 1 && r != 2 &&  r != 3);
        return r;
}
 

here are the warnings i am getting:
warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
at the arrow

and i get the menu to work , but when i upload it the the website it loops infinitely

[ckking]

ok, i changed it because the infinite loop was caused by the upload site having the loop first