// https://omegaup.com/arena/problem/Detectando-el-orden 
#include <stdio.h> 
 
int main( ) { 
   int a, b, c; 
   scanf("%d%d%d", &a, &b, &c); 

    if (a == b && b == c) { 
      printf("I"); 
   } else if (a <= b && b <= c) { 
      printf("C"); 
   } else if (a >= b && b >= c) { 
      printf("D"); 
   } else { 
      printf("X"); 
   } 
}