/* Amazon donates 0.5% of the price of eligible 
AmazonSmile purchases to the charitable organization of user's choice.

Write a program that first reads the number of items user purchased, 
then the program reads a price for each item and the eligibility indicator, 
1 or 0 (1 means item is eligible for AmazonSmile and 0 otherwise). 
The program finds the donation amount the charity will receive from 
this purchase. 

Testing the program:
Test 1: num_items=-5
Test 2: num_items=5 prices/indicators: 1.99 1 5.99 0 3.99 0 2.99 1 3.99 1
donation=1.99*0.5/100+2.99*0.5/100+3.99*0.5/100=0.04485
Test 3: num_items=3 prices/indicators: 5.99 0 3.99 0 1.99 0
donation=0.0


*/
#include<stdio.h>
int main(){
	int num_items, i=0,indicator;
	double price, donation=0.0;
	printf("enter number of items\n");
	scanf("%d",&num_items);
	if(num_items>0){
		printf("enter %d prices and indicators\n",num_items);
		while(i<num_items){
			scanf("%lf%d",&price, &indicator);
			if(indicator==1)
				donation+=price*0.5/100;
			i++;
		}
		printf("donation %f\n",donation);
	}
	else
		printf("didn't buy anything\n");
	return 0;
}