Set a relative path for crystal reports

I have written the following code,

CrystalDecisions.CrystalReports.Engine.ReportDocument report = new CrystalDecisions.CrystalReports.Engine.ReportDocument();
report.Load(@"C:\Users\XXX\Desktop\Backup1\Project\ReportsFolder\ReportSalesInvoice.rpt");

Report works fine for the above code But I want to give a relative path so I can install it in several machines without changing the path. I have also tried the following paths

string loc = AppDomain.CurrentDomain.BaseDirectory;
string loc2 = Application.StartupPath;
string loc3 = Application.UserAppDataPath;
string loc4 = Application.CommonAppDataPath;

Used them as,

report.Load(loc2 + "\\ReportSalesInvoice.rpt");

But the file cannot be accessed.Please Help.