Scanf using \n. Don't know what does it do

I am new to programming and I can't figure out what is happening. This is my code:

#include <iostream>
#include <stdio.h>
using namespace std;

int main(){
   int c,d;
   scanf("%d\n", &c);
   cout<<c<<endl;
   return 0;
}

I can't understand why it's taking two inputs and printing the first one out.