text: #include<stdio.h>
  #include<string.h>
  #include<stdlib.h>
  
  char grade(int score);
  
  int main(int argc, char** argv)
  {
      
      int a = atoi(argv[1]);
      char output = grade(a);
      printf("return:%c\n", output);
      return 1;
  }
  
  
  
  char grade(int score){
      char result = 'A';
      if(score > 90) result = 'A';
      if(score > 80) result = 'B';
      result = 'C';
      return result;
  }