C :

#include<stdio.h>
int main()
{
	int score;
	while(scanf("%d",&score)!=EOF)
	{
		if(score>=90)
			printf("A\n");
		else if(score>=80&&score<=89)
			printf("B\n");
		else if(score>=70&&score<=79)
			printf("C\n");
		else if(score>=60&&score<=69)
			printf("D\n");
		else 
			printf("E\n");
	}
	return 0;
}

C++ :

#include<stdio.h>
#include<math.h>
int main()
{
	int x;
	scanf("%d",&x);
	if(x>=90)
		printf("A\n");
	else if(x>=80&&x<90)
		printf("B\n");
	else if(x>=70&&x<80)
	    printf("C\n");
	else if(x>=60&&x<70)
		printf("D\n");
	else
		printf("E\n");
	return 0;
}

Pascal :

var n:integer;
begin
readln(n);
  if n>=90 then write('A');
  if (n>=80) and (n<=89) then write('B');
  if (n>=70) and (n<=79) then write('C');
  if (n>=60) and (n<=69) then write('D');
  if n<60 then write('E');
end.