#include <stdio.h>

int main(void) {
	int play, win, sum, i;
	double perc;
	while( scanf("%d%d%lf",&play,&win,&perc), play+win+perc) {
		int bets[100] = {0};
		sum = 0;
		for(i = 0; i < play; i++ ) {	
			scanf("%d",&bets[i]);
			sum += bets[i]*100;
		}
		perc = sum*(100 - perc)/100/bets[win-1];
		printf("%d\n",perc);
	}
	return 0;
}