#include<stdio.h>

int main()
{
	double n,a[12],max;
	int i;
	scanf("%lf",&n);
	for(i=0;i<12;i++)
		scanf("%lf",&a[i]);
	max=a[0];
	for(i=1;i<12;i++)
		if(max<a[i])
			max=a[i];
	printf("%.2lf\n",n*max);
	return 0;
}
/**************************************************************
	Problem: 2031
	User: admin
	Language: C
	Result: Accepted
	Time:8 ms
	Memory:1144 kb
****************************************************************/