determine largest number of 4 values!

#include <iostream>

using namespace std;

int _max(int x1, int x2)
{
    if(x1 > x2)
        return x1;
    else
        return x2;
}

int main()
{
    int a, b, c, d;

    cout << "insert the values: ";
    cin >> a >> b >> c >> d;

    int comparison;
    int second_comparison;
    int last_comparison;

    comparison = _max(a, b);
    second_comparison = _max(comparison, c);
    last_comparison = _max(second_comparison, d);

    cout << last_comparison << "\n";

    return 0;
}