Confused on prototype function help please.

[Spacemanspalds]

I wrote this basic program to provide a remainder of two numbers divided and it works fine. But I'm supposed to make this a prototype function, I've looked online everywhere trying to get it right. I want to designate it as a custom function, but I'm apparently not putting it in correctly.


[/int main(){

int a,b,r;
cout<<"\n This program will take your first number and \n divide it by the second number and give you the remainder.\n Enter the 1st number..."<< a;
cin>> a;
cout<<"Enter the second number..."<<b;
cin>>b;

r=a%b;

cout<<"\nThe remainder is..."<< r<<'\n';

}]

[helios]

//This is a prototype, or function declaration. 
int sum(int a, int b);
//Note: the parameter names in the prototype don't have to match the ones in the definition.
//For example: int sum(int, int);
//Using a prototype lets you define functions in any order, which is useful for example
//in the case of mutually recursive functions.

int main(){
    int a = sum(1, 2);
}

//This is the definition. The parameter and return types must match the prototype,
//otherwise you'll get errors when you try to compile.
int sum(int d, int e){
    return d + e;
}