#include <stdio.h>
int main(void){
int N,H,L;
scanf("%d %d %d %d",&N,&H,&L,&i);
for(i=0;i<N+H+L;i++){
  if(i==1){
    printf("IMPOSSIBLE");
  }
  else(i != 1){
    printf("POSSIBLE");
  }
  return 0;
}
  printf("%d %d %d %i",&N,&H,&L,&i);
  return 0;
}