How to Find the Largest Number in the User Defined Number Using 1-D array in C++

#include <iostream>

using namespace std;

int main()
{
    int size,i;
    int arrayname[size];
    cout<<"Enter The number Of values."<<endl;
    cin>>arrayname[size];
    cout<<"Enter The Values : "<<endl;
    for(i=0 ; i<size ; i++)
    {
        cin>>arrayname[i];
    }
    int max=arrayname[0];
    for(i=0 ; i<size ; i++){
    if(max<arrayname[i]){
    max=arrayname[i];}
    }
    cout << "Maximum Number is : " <<max<< endl;
    return 0;
}