这个咋解决，读取数据无效

#include
using namespace std;
int main()
{
long int *mt,*en,*ph,i,*sum,*as;
long int a,b,c,d,e;
cout << "请输入所要等级成绩的人数\n";
cin >> a;
b = a; c = a; d = a; e = a;
mt= new long int[a];
en= new long int[b];
ph=new long int[c];
sum = new long int[d];
as = new long int[e];
for (i = 0; i < a && a<30 ; i++)
cin >> mt[i] >> en[i] >> ph[i];
sum[i] = mt[i] + en[i] + ph[i];
as[i] = sum[i] / 3;
cout << sum[i] << " " << as[i] << endl;