70pts求助

#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,p,q;
inline char fgc(){
// 	return getchar();
    static char buf[1<<17],*p=buf,*q=buf;
    return p==q&&(q=buf+fread(p=buf,1,1<<17,stdin),p==q)
    ?EOF:*p++;
}
inline int rint(){
    int x=0,s=fgc(),f=1;
    for (;s<'0'||'9'<s;s=fgc())f=s=='-'?-f:f;
    for (;'0'<=s&&s<='9';s=fgc())x=x*10+(s^'0');
    return x*f;
}
int work(int a,int b){
	return b*q+pow(a/(b+1),2)*(a-a%(b+1)*(a/(b+1)+1))*p+pow(a/(b+1)+1,2)*(a%(b+1))*p;
}
signed main(){
	n=rint(),p=rint(),q=rint();
	int ans=1e17;
	for(int i=n;i>=0;i--){
//		cout<<work(i,n-i)<<' '<<i<<' '<<n-i<<'\n';
		ans=min(ans,work(i,n-i)>=0?work(i,n-i):(int)1e17);
	}
	cout<<ans;
	return 0;
}