【HDU1009】FatMouse'Trade

FatMouse prepared M pounds of cat food, ready to trade with the cats guarding the warehouse containing his favorite food, JavaBean. 
The warehouse has N rooms. The i-th room contains J[i] pounds of JavaBeans and requires F[i] pounds of cat food. FatMouse does not have to trade for all the JavaBeans in the room, instead, he may get J[i]* a% pounds of JavaBeans if he pays F[i]* a% pounds of cat food. Here a is a real number. Now he is assigning this homework to you: tell him the maximum amount of JavaBeans he can obtain. 

The input consists of multiple test cases. Each test case begins with a line containing two non-negative integers M and N. Then N lines follow, each contains two non-negative integers J[i] and F[i] respectively. The last test case is followed by two -1‘s. All integers are not greater than 1000. 

For each test case, print in a single line a real number accurate up to 3 decimal places, which is the maximum amount of JavaBeans that FatMouse can obtain. 

#include 
#include 
using namespace std;
int n,u;
double m,ans;
struct room
{
    double j,f,p;
} r[1005];
int cmp(room a,room b)
{
    return a.p>b.p;
}
int main()
{
    while(scanf("%lf%d",&m,&n)&&n!=-1&&m!=-1)
    {
        for(int i=0;im) ans+=m*r[u].p,m=0;
//剩下的猫粮不够把这个房间的咖啡豆换过来，那就能换多少换多少
            else ans+=r[u].j,m-=r[u].f;
//够的话，这间房子全部咖啡豆换过来
            u++;
        }
//        while(m>=r[u].f&&u