public static int minimumLoss(List<long> price)
{
    var loss = long.MaxValue;

    var priceList = price.Select((v, i) => new { Key = v, Value = i })
        .ToDictionary(x => x.Key, x => x.Value)
        .OrderByDescending(x => x.Key)
        .ToList();

    for ( var i = 0; i < price.Count - 1; i++)
    {
        var priceYearNow = priceList[i];
        var priceYearNext = priceList[i + 1];

        if (priceYearNow.Value < priceYearNext.Value)
        {
            var diff = (priceYearNow.Key - priceYearNext.Key);
            loss = Math.Min(loss, diff);
        }
    }

    return (int)loss;
}