text: #include <iostream>
  using namespace std;
  int main ()
  {
  	int marks;
  	cout <<"enter your marks. ";
  	cin>>marks;
  	if (marks>=90)
  	cout <<"A grade";
  		else 
  			if(marks>=90)
  			cout<<"B grade";
  				else
  					if(marks>=80)
  					cout<<"C grade";
  						else
  							if (marks>=70)
  							cout<<"D grade";
  								else 
  								cout<<"F grade.";
  	return 0;							
  				
  }
  