#include <stdio.h>
int main() {
	double N, T, m, n, sum = 0;
	double price = 0;
	double arr[1100][2] = { 0 };
	scanf("%lf %lf", &N, &T);
	for (int i = 1; i < N + 1; i++) {
		scanf("%lf %lf", &m, &n);
		arr[i][0] = m;
		arr[i][1] = n;
	}
	for (int j = 1; j < N; j++) {
		for (int m = j + 1; m < N + 1; m++) {
			if (arr[j][1] / arr[j][0] < arr[m][1] / arr[m][0]) {
				double x, y;
				x = arr[j][1];
				y = arr[j][0];
				arr[m][1] = arr[j][1];
				arr[m][0] = arr[j][0];
				arr[j][1] = x;
				arr[j][0] = y;
			}
		}
	}
	for (int i = 1; i < N + 1; i++) {
		if (sum + arr[i][0] < T) {
			sum += arr[i][0];
			price += arr[i][1];
		}
		else {
			price += (T - sum) * (arr[i][1] / arr[i][0]);
			break;
		}
	}
	printf("%.2lf", price);
    return 0;
}