Using default arguments to archive overloading in functions

In recent days, I began leaning C++. And this is my first work.

#include <iostream>
#include <limits.h>

using namespace std;
int max(int, int, int c=sizeof(INT_MIN));
int main()
{
    cout << "Enter 3 digits:" << endl;
    int a,b,c;
    cin >> a >> b >> c;
    cout << "The max of 3 digits is " << max(a,b,c) << endl;
    cout << "The bigger one of first 2 digits is " << max(a,b) << endl;
    return 0;
}

int max(int a, int b, int c)
{
    if(b>a)
        a=b;
    if(c>a)
        a=c;
    return a;
}