function fkmt = kme_at_50(dt)
% this function performs Kaplan-Meier estimation with given parameter
% and gives estimated F(50.0)
[kmest sortdat] = KMcdfSM(dt(:,1), dt(:,2), 0);
fkmt = kmest(sum(50.0 >= sortdat), 1); %this gives F(50.0)