P[s-E[s] = 400-E/s ;p>1/2] <= P[P[s-E[s] <= 400-E[s];p>1/2]
= P[|E[s]-s| >= E[s]-400;p>1/2]
P[|E[s]-s| >= E[s]-400;p>1/2] <= var[s]/(E[s]-400)^2 = f(p) <= max f(p) p>1/2
var[s] = 1000p(1-p)
