[开发工具]C++分配动态内存

为什么命名就分配不了那么多内存，还是显示内存分配成功

#include<iostream>
#include<cstdlib>
using namespace std;
int main()
{
    int n ;
    cout << "input a number:" << sizeof(n);
    cin >> n;

    int* a = new(nothrow) int[n];
    if(a==NULL){
        cout << n*sizeof(int) << "allocate failure" << endl;
    }else{
        cout << "allocate success" << endl;
    }

    delete[] a;
}