public class Solution {
public double AverageWaitingTime(int[][] customers)
{
List wTime = new List();
int startTime = 0;
int endTime = 0;

foreach (var i in customers)
{
startTime = Math.Max(i[0], endTime);
endTime = startTime + i[1];
wTime.Add(endTime - i[0]);
}

return Math.Round(wTime.Average(), 5);
}
}

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