#include<stdio.h>
#include<algorithm>
using namespace std;
#define M 1002
struct node
{
int j,f;
};
struct node jf[M];
bool cmp(
const node &a,
const node &
b)
{
return 1.0 * a.j / a.f >
1.0 * b.j /
b.f;
}
int main()
{
// freopen("in.txt","r",stdin);
int m,n;
double s;
while(scanf(
"%d%d",&m,&n) + m +
n)
{
for(
int i=
0; i<n; i++
)
{
scanf("%d%d",&jf[i].j,&
jf[i].f);
}
sort(jf,jf +
n,cmp);
s = i =
0;
while(m>
0 && i<
n)
{
if(m >=
jf[i].f)
s +=
jf[i].j;
else
s +=
1.0 * m / jf[i].f *
jf[i].j;
m -=
jf[i].f;
i++
;
}
printf("%.3lf\n",s);
}
return 0;
}
转载于:https://www.cnblogs.com/lk1993/p/3258991.html
