C :

#include<stdio.h>
int main()
{
    double fraction;
    while ( scanf ( "%lf", &fraction ) != EOF )
    {
        if(fraction<=59&&fraction>=0) printf("E\n");
        else if(fraction<=69&&fraction>=60) printf("D\n");
        else if(fraction<=79&&fraction>=70) printf("C\n");
        else if(fraction<=89&&fraction>=80) printf("B\n");
        else if(fraction<=100&&fraction>=90) printf("A\n");
        else printf("Score is error!\n");
    }
    return 0;
}