#include<stdio.h>
#include<math.h>
int main()
{
	int n, t,avgmax=-1,s;
	double sum=0;
	struct a {
		double m;
		double v;
		double avg;
	}p[105];
	scanf("%d%d", &n, &t);
	for (int i = 0; i < n; i++) {
		scanf("%lf%lf", &p[i].m, &p[i].v);
		p[i].avg = p[i].v / p[i].m;
	}
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			if (p[j].avg > avgmax) {
				s = j;
			}
		}
		avgmax = -1;
		double q = p[s].avg;
		p[s].avg = -1;
		
		if (t > p[i].m) {
			t -= p[i].m;
			sum += p[s].v;
		}
		else if(t== p[i].m) {
			t -= p[i].m;
			sum += p[s].v;
			break;
		}else{
			sum += q * t;
			break;
		}
	}
		printf("%.2lf", sum);
		return 0;
}

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