Clear[Reps,M0,Succes,i,i];{Reps,M0}={1000,100};For[i=1;Succes=0,i≤Reps,i++,M=M0;While[0<M&&M<200,If[Random[UniformDistribution[{0,1}]]≤1/5,M=M+4,M=M-1]];If[M≥200,Succes=Succes+1]];N[Succes/Reps]