Code:

#include <bits/stdc++.h>
#define mod 1000000007
using namespace std;
int main()
{
	int n;
	cin >> n;
	int j;
	double p,sum = 0;
	for (int i = 1; i <= n; i++)
	{
		cin >> p >> j;
		sum += p * 0.85 * j;
	}
	printf("%.1lf",sum);
	return 0;
}