Saving HDU

题目链接：

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AC代码：

#include<bits/stdc++.h>using namespace std;struct aa{    int vi,m;}a[1000];bool cmp(aa x,aa y){    return x.vi>y.vi;}int main(){    int v,n,sum;    while(~scanf("%d",&v)&&v)//多组输入，并且v不为零，若v为零则break;    {        scanf("%d",&n);        sum=0;        for(int i=0;i<n;i++)            scanf("%d %d",&a[i].vi,&a[i].m);        sort(a,a+n,cmp);        for(int i=0;i<n;i++)        {            if(v-a[i].m>=0)            {                sum+=a[i].vi*a[i].m;                v=v-a[i].m;            }            else            {                sum+=v*a[i].vi;                break;            }        }        printf("%d\n",sum);    }}