#include <stdio.h>

int main(void)
{
	char str[100];
	while(scanf("%s",str)==1){
		int state = 0;
		int len = strlen(str);
		int i;
		for(i=0;i<len;i++){
			switch(str[i]){
			case 'D':state++;break;
			case 'U':if(state > 0)state--;break;
			}
		}
		if(state==0)printf("1F\n");
		else printf("B%dF\n",state);
	}
	return 0;
}