#include <iostream>

using namespace std;

int sum(int a, int b=10, int c=20);

int main(){

/* In this case a value is passed as

* 1 and b and c values are taken from

* default arguments.

*/

cout<<sum(1)<<endl;

/* In this case a value is passed as

* 1 and b value as 2, value of c values is

* taken from default arguments.

*/

cout<<sum(1, 2)<<endl;

/* In this case all the three values are

* passed during function call, hence no

* default arguments have been used.

*/

cout<<sum(1, 2, 3)<<endl;

return 0;

}

int sum(int a, int b, int c){

int z;

z = a+b+c;

return z;

}