能举一个反例吗？

#include<bits/stdc++.h>
using namespace std;
int s1,s2,s3,s4,f1,f2,ans;
int a[114],b[114],c[114],d[114];
bool cmp(int x,int y){return x>y;}
void f(){ans+=max(f1,f2);return;}
int main(){
    ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>s1>>s2>>s3>>s4;
	for(int i=1;i<=s1;i++)cin>>a[i];
	for(int i=1;i<=s2;i++)cin>>b[i];
	for(int i=1;i<=s3;i++)cin>>c[i];
	for(int i=1;i<=s4;i++)cin>>d[i];
	sort(a+1,a+s1+1,cmp);
	sort(b+1,b+s2+1,cmp);
	sort(c+1,c+s3+1,cmp);
	sort(d+1,d+s4+1,cmp);
	for(int i=1;i<=s1;i++){
		if(f1<=f2)f1+=a[i];//左脑用时少加左脑 
		else f2+=a[i];//右脑用时少加右脑
	}f();
	f1=0,f2=0;
	for(int i=1;i<=s2;i++){
		if(f1<=f2)f1+=b[i];
		else f2+=b[i];
	}f();
	f1=0,f2=0;
	for(int i=1;i<=s3;i++){
		if(f1<=f2)f1+=c[i];
		else f2+=c[i];
	}f();
	f1=0,f2=0;
	for(int i=1;i<=s4;i++){
		if(f1<=f2)f1+=d[i];
		else f2+=d[i];
	}f();
	f1=0,f2=0;
	cout<<ans;
	return 0;
}