C++ :: Sorting A User Input For Array?

Were supposed to be able to sort an array which is user input, but the first number they input is supposed to be the length of the array, and everything after that is the actual array.

Here is my code:

#include <iostream>
#include <iomanip>
using namespace std;
int main() {
int size;
int list[80];
bool isSorted (const int list[], int size);

[code]....

I'm stuck on how I'm supposed to use the first digit of input for the array size.