Console.InputEncoding = Encoding.Unicode;
Console.OutputEncoding = Encoding.Unicode;

Console.Write( "Input start gold value : " );
string goldValueRaw = Console.ReadLine();
int goldValue = int.Parse( goldValueRaw );

Console.Write( "Input start crystals value : " );
string crystalsValueRaw = Console.ReadLine();
int crystalsValue = int.Parse( crystalsValueRaw );

Console.Write( "Input crystals price : " );
string crystalPriceRaw = Console.ReadLine();
int crystalPrice = int.Parse( crystalPriceRaw );

bool loopExitFlag = false;

while ( !loopExitFlag )
{
    Console.WriteLine( $"Gold = {goldValue}, Cry = {crystalsValue}\n" );
    Console.Write( "Buy crystals, input count : " );
    string buyCrystalsCountRaw = Console.ReadLine();
    int buyCrystalsCount = int.Parse( buyCrystalsCountRaw );

    goldValue -= buyCrystalsCount * crystalPrice;
    crystalsValue += buyCrystalsCount;

    Console.WriteLine( "Continue? Enter 'n' for exit" );
    string continueAnswer = Console.ReadLine();
    string exitAnswer = "n";

    loopExitFlag = string.Equals( continueAnswer, exitAnswer );
}