#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>

struct Info {
	int m;
	int v;
	double per;
};

int cmp(const void *a, const void *b);

int main() {
	int n, t;
	scanf("%d%d", &n, &t);
	struct Info *info = (struct Info *)malloc(sizeof(struct Info) * n);
	for (int i = 0; i < n; i++) { 
		scanf("%d%d", &info[i].m, &info[i].v);
		info[i].per = (double)info[i].v / info[i].m;
	}
	qsort(info, n, sizeof(struct Info), cmp); 
	double cnt = 0;
	int i;
	for (i = 0; i < n && t - info[i].m >= 0; i++) { 
		cnt += info[i].v; 
		t -= info[i].m;
	}
	if (i < n)  
		cnt += t * info[i].per;
	printf("%.2f", cnt);
	return 0;
}

int cmp(const void *a, const void *b) { 
	return (*(struct Info *)b).per - (*(struct Info *)a).per;
}