fun <- function(x,y){
    exp(-x*x+y)
    }
area <- 4.5
N <- 100000 # total number of random points we will get
j <- 1 # is the number of the random point we are finding
sum <- 0
while (j<=N){
    x <- runif(1,-1,2)
    y <- runif(1,0,4)
    if (x^2<y & y<x+2){ # then it will be in our region
        sum <- sum + fun(x,y)
        j <- j + 1
        }
    }
avg <- sum/N
paste('Our approximation is :',avg*area)