par(mfrow=c(2,2))
for(i in 1:4)
{
l<-20;
x<-1:l;
y<-2*floor(2*runif(l))-1;
z<-cumsum(y);
plot(x,z,type="l",ylim=c(-l/2,l/2),xlab="Liczba prób",ylab="Liczba wygranych")
lines(x=c(0,2*l),y=c(0,0),lwd=1,col="blue");
for(i in 1:l)
{
if(z[i]>=0)
{
lines(x[i],z[i],type="p",col="green")
}
else
{
lines(x[i],z[i],type="p",col="red")
}
}
}