q求t条

#include<bits/stdc++.h>
using namespace std;
int n,m,sum;
struct milk{
    int dj,zl;
}a[10005];
bool cmp(milk x,milk y){
    if (x.dj!=y.dj) {
        return x.dj<y.dj;
    }

}
int main(){
    cin>>n>>m;
    for (int i=1;i<=m;i++){
        cin>>a[i].dj>>a[i].zl;
    }
    sort(a+1,a+n+1,cmp);
    for (int i=1;i<=m;i++) {
        if (n>=a[i].zl) {
            sum+=a[i].dj*a[i].zl;
            n-=a[i].zl;
        }
        else {
            sum+=a[i].dj*n;
            break;
        }
    }
    cout<<sum;
    return 0;
}