g<-function(x,y,n){
x**(n/2)*exp(-x/2)-y**(n/2)*exp(-y/2)
}

n<-5
c1<-0.1
f<-function(x){g(x,c1,n)}
c2<-uniroot(f,interval=c(n,100))$root
c2

p<-1-pchisq(c2,n)+pchisq(c1,n)


myquantile<-function(alpha,n){
repp<-20000
res<-rep(0,repp)
resx<-rep(0,repp)
for (i in 1:repp){
c1<-0.001*i
f<-function(x){g(x,c1,n)}
c2<-uniroot(f,interval=c(n,100))$root
p<-1-pchisq(c2,n)+pchisq(c1,n)
res[i]<-p
resx[i]<-0.01*i
i<-ifelse(p-0.05<= 0,i,break) 
}
return(c(c1,c2,p))
}

myquantile2<-function(alpha,n){
repp<-20000
res<-rep(0,repp)
resx<-rep(0,repp)
for (i in 1:repp){
c1<-n-0.001*i
f<-function(x){g(x,c1,n)}
c2<-uniroot(f,interval=c(n,100))$root
p<-1-pchisq(c2,n)+pchisq(c1,n)
res[i]<-p
resx[i]<-0.01*i
i<-ifelse(p-0.05>= 0,i,break) 
}
return(c(c1,c2,p))
}