#include <cstdio>

typedef __int64 LL;

int main()
{
	int n, v;
	LL s, r;

	while(scanf("%d", &n), n){
		//initialize
		r = s = 0;
		//input and process
		while(n--){
			scanf("%d", &v);
			r += s < 0 ? -s : s;
			s += v;
		}
		//print result
		printf("%I64d\n", r);
	}
	return 0;	
}