Помогите пожалуйста решить

#include <algorithm>
#include <iostream>
#include <iomanip>
#include <random>
#include <vector>
#include <iterator>
#include <numeric>
#include <cstdlib>
using namespace std;
int main() {
uniform_int_distribution<> uid(-32, 32);
mt19937 gen{ random_device()() };
auto rand = [&] { return uid(gen); };
const auto length = 12;
vector<int> box(length);
generate(box.begin(), box.end(), rand);
copy(box.begin(), box.end(), ostream_iterator<int>(cout, " "));
puts("");
auto max = *max_element(box.begin(), box.end());
auto positive = [](int x) { return x > 0; };
if (find_if(box.begin(), box.end(), positive) != box.end()) cout << "max: " << max << '\n';
else puts("Positive not found!");
auto product = accumulate(box.begin(), box.end(), 1LL, multiplies<>());
cout << "product: " << product << '\n';
vector<int> pos;
copy_if(box.begin(), box.end(), back_inserter(pos), positive);
cout << "positive: ";
copy(pos.begin(), pos.end(), ostream_iterator<int>(cout, " "));
puts("");
system("pause > nul");
}

#include < iostream >
#include < vector >
#include < random >
#include < ctime >

using namespace std;

void fillWithRandoms(vector< double > &a_, int N){
srand(time(NULL));
while(N--)
a_.push_back(rand() % 21 - 10);
}

double findMaxPositiveElement(vector< double > &a_){
double res = 0;
for(auto &i: a_)
res = max(res, i);
return res;
}

double productOfVector(vector< double > &a_){
double res = 1;
for(auto &i: a_)
res *= i;
return res;
}

void showPositiveElements(vector< double > &a_){
for(auto &i: a_)
if(i > 0)
cout << i << " ";
}

int main(){
int n;
cin >> n;
vector< double > a;
fillWithRandoms(a, n);
cout << "Vector a = ";
for(auto &i: a) cout << i << " ";
double positiveMax = findMaxPositiveElement(a);
if(positiveMax > 0)
cout << "\nMax positive element = " << positiveMax;
else
cout << "\nThere are no positive elements in the vector";
double vectorProduct = productOfVector(a);
cout << "\nProduct of vector elements = " << vectorProduct;
cout << "\nPositive elements in vector: ";
showPositiveElements(a);
}