问题标题: 酷町堂：2364 班级统分

#include<iostream>
#include<math.h>
#include<cstdio>
#include<cmath>
using namespace std;
int main(){
    long long Y,S,E,J;
    cin>>Y>>S>>E>>J;
    long long maxn=0,minn=144321320;
    maxn=max(Y,maxn);
    maxn=max(S,maxn);
    maxn=max(E,maxn);
    maxn=max(J,maxn);
    minn=max(Y,minn);
    minn=max(S,minn);
    minn=max(E,minn);
    minn=max(J,minn);
    if((Y+S+E+J)/4>90){
        cout<<"A";
    } 
    else if((Y+S+E)/3&&J>=90){
        cout<<"B";
    }
    else if(maxn==100&&minn>=60){
        cout<<"D";
    }
}

代码哪里错了