Dynamic Memory C++ problem

Question

The code provided calculates the largest element of the array nums and outputs it.
Complete the code to declare the nums array and take the array elements as input.
The array can be of any variable size, so the first input should be the size of the array, followed by its elements.

This is my code:
#include <iostream>
using namespace std;

int main() {
int n;
cin>>n; //size of the array
//your code goes here
int nums[n];
while(n>0){
int x;
cin>>x;
nums[n-1] = x;
n--;
}

int max = nums[0];
for(int i=0; i<n; i++) {
if(nums[i]>max)
max = nums[i];
}
cout << max;

return 0;
}

It passed 4 of the 5 tests. Can someone please explain what is wrong with this code ? Thank you.