C++ 初学者关于 getline 的问题

大家好，我的问题是这个程序的第一个for loop里面只能输入第一次的信息，第一次循环后就会自动跳过接下来输入流程直接到最后结果，实在不知道该怎么办。求救呀！！！！
#include <iostream>

using namespace std;

int main()
{
    const int size1 = 5, size2 = 4;
    char check;

    string student[size1];
    int grade[size1][size2];

    for(int c=0; c<=4; c++)
    {
        cout<< "Student" << c+1 << " name: ";
        getline(cin,student[c]);


        cout << "Grade: ";
        do
        {
            check = 'y';
            for(int d=0; d<=3; d++)
            {
                cin >> grade[c][d];
                if(grade[c][d]<0 || grade[c][d]>100)
                    check = 'n';
            }

            if(check == 'n')
            {
                cout << "Invalid grade. Enter again.\n";
                cout << "Grade: ";
            }
        }while(check == 'n');

    }

    int sum;
    double average;
    char letter;

    for (int c=0; c<=4; c++)
    {
        sum = 1;
        for(int d=0; d<=3; d++)
            sum += grade[c][d];
        average = sum/4.00;

        if(average>=90 && average <=100)
            letter = 'A';
        else if(average>=80 && average<90)
            letter = 'B';
        else if(average>=70 && average<80)
            letter = 'C';
        else if(average>=60 && average<70)
            letter = 'D';
        else if(average>=0 && average<60)
            letter = 'F';

        cout << "Student name: " << student[c]<<endl;
        cout << "Average grade: " << average<<endl;
        cout << "Letter grade: " << letter<<endl;
        cout << "----------------------------";
        cout << endl;
    }
}