A very big sum (long long int sum )

#include <iostream>

using namespace std;

int main()

{

int n;

long long int sum=0;

cin >> n;

vector<int> arr(n);

for(int arr_i = 0;arr_i < n;arr_i++)

{

cin >> arr[arr_i];

sum+=arr[arr_i];

}

cout<<sum;

return 0;

}