#include <iostream>
using namespace std;

int N, M, P[11];

int main() {
	while (1) {
		cin >> N >> M;
		if (!(N | M)) break;
		memset(P, 0, sizeof(P));
		for (int i = 0; i < N; i++) {
			int d, p; cin >> d >> p;
			P[p] += d;
		}
		for (int i = 10; i; i--) {
			if (P[i] < M) {
				M -= P[i]; P[i] = 0;
			} else {
				P[i] -= M; M = 0; break;
			}
		}
		int s = 0;
		for (int i = 0; i <= 10; i++)
		 s += i * P[i];
		cout << s << endl;
	}
	return 0;
}