#include <stdio.h>

int nodeval() {
	int nc, nd, d, i, sum, child[100];
	sum = 0;
	if (scanf("%d %d", &nc, &nd) == 2) {
		for (i = 1; i <= nc; ++i) {
			child[i] = nodeval();
		}
		for (i = 0; i < nd; ++i) {
			if (scanf("%d", &d) == 1) {
				if (nc) {
					if (1 <= d && d <= nc) {
						sum += child[d];
					}
				}
				else sum += d;
			}
		}
	}
	return sum;
}

int main(int argc, char *argv[]) {
	printf("%d\n", nodeval());
	return 0;
}