q;float f(p,n){return n<23?p/200.*(1+f(p<q?0:p-q,++n))+(100-p)/300.*(1+f(p>100-q?100:p+q,n)):0;}main(p){q=!printf("%.9f",(f(p,scanf("%d%d",&p,&q))+1)/3);}