题解 100% AC

#include <bits/stdc++.h>
using namespace std;
int main(){
    int a,b,c,d,k,ans=0;cin>>a>>b>>c>>d>>k;
    if(d>=k) cout<<k*4;
    else{
        ans+=d*4;
        k-=d;
    	if(c>=k) cout<<ans+k*3;
        else{
        	ans+=c*3;
            k-=c;
            if(b>=k) cout<<ans+k*2;
        	else{
        		ans+=b*2;
        	    k-=b;
                if(a>=k) cout<<ans+k;
        		else{
        			ans+=a;
        		    k-=a;
                    cout<<ans;
                    return 0;
        		}
        	}
        }
    }
	return 0;
}