#include<iostream>
#include<string>
#include<fstream>
#include<iomanip>
using namespace std ;

string marks;
 int id [100], stdid,Tot;

 string name[100], stdname;
 float mark[100], stdmark,ave,sum;

int main()
{


	ifstream infile ;

	cout<<"Please enter file name containing students marks:"<<endl;
	cin>>marks;

	infile.open(marks);

	if(!infile)
	{
	cout<<"can not open "<<endl;
	return 1;
	}


	int i=0;
	infile>>stdid>> stdname>> stdmark;

    while( infile)

    { 
    id [i] = stdid;
	name[i]=stdname;
	mark[i]=stdmark;

	Tot=i;
	mark[i]++;
	ave= mark[i]++/i;

	infile>>stdid >> stdname>> stdmark;
	}

	for(int j=0 ; j <= Tot ; j ++ ) //standard deviation  calculation 
	{
		sum=0;
		sum=(mark[j] - ave) * ( mark[j] - ave) /  (Tot - 1 );
		sum++;
	}

	cout<<"The distribution of the marks are: "<<endl;
    cout<<"ID"<<setw(4)<<"Name"<<setw(4)<<"Grade"<<setw(4)<<"Letter Grade"<<endl;
    cout<<"=== ===== ===== ========="<<endl;

	for ( int a=0 ; a <= a-1 ; a++)
	{
		if ( mark[a] < ( ave - 3/2 *sum ) )

			cout <<id[a]<<name[a]<<mark[a]<<"F"<<endl;
	}

	
	for ( int a=0 ; a <= a-1 ; a++)
	{
		if (     (  mark[a] <=  ( ave - 3/2 *sum ) )    ||  (  mark[a] >  ( ave - 1/2 *sum ) )   )

			cout <<id[a]<<name[a]<<mark[a]<<"D"<<endl;
	}


    for ( int a=0 ; a <= a-1 ; a++)
	{
		if (     (  mark[a] >=  ( ave - 1/2 *sum ) )  ||  (  mark[a] <  ( ave - 1/2 *sum ))    )

			cout <<id[a]<<name[a]<<mark[a]<<"C"<<endl;
	}


    for ( int a=0 ; a <= a-1 ; a++)
	{
		if (     (  mark[a] <= ( ave + 1/2 *sum ) )  ||  (  mark[a] >  ( ave + 3/2 *sum ))    )

			cout <<id[a]<<name[a]<<mark[a]<<"B"<<endl;
	}


	for ( int a=0 ; a <= a-1 ; a++)
	{
		if (  mark[a] >=  ( ave + 3/2 *sum ))

			cout <<id[a]<<name[a]<<mark[a]<<"A"<<endl;
	}
InFile.close();
	system ("Pause");
	return 0;
}