prefixSum(l, r)

int calculated[10000];
int preCalculate(int arr[], int n){
    calculated[0]= arr[0];
    for (int i = 1; i < n; ++i)
    {
        calculated[i] = calculated[i-1] + arr[i];
    }
}

int prefixSum(int l, int r){ 
    if(l != 0){
        return calculated[r] - calculated[l-1];
    }else{
        return calculated[r];
    }
}