杭电2004成绩转换

#include<iostream>
using namespace std;
int main(int argc, const char * argv[]) {
    int a;
    while (cin>>a) {
    if((a>90||a==90)&&(a<100||a==100)) cout<<"A"<<endl;
    else if((a>80||a==80)&&(a<89||a==89)) cout<<"B"<<endl;
    else if((a>70||a==70)&&(a<79||a==79)) cout<<"C"<<endl;
    else if((a>60||a==60)&&(a<69||a==69)) cout<<"D"<<endl;
    else if((a>0||a==0)&&(a<59||a==59)) cout<<"E"<<endl;
    else cout<<"Score is error!"<<endl;
    }
    return 0;

}