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