b=1.
fb=f(b)
n=10000000
ns=0
do i=1,n
xj=rand(0)*b
yj=rand(0)*fb
y=f(xj)
if(y.ge.yj)then
ns=ns+1
endif
enddo

print *,ns*b*fb/n
stop

end


function f(x)
f=x*x
return
end