def dfs(i, sum, a, k):
if i == len(a):
return sum == k
if dfs(i+1, sum, a, k):
return True
if dfs(i+1, sum+a[i], a, k):
return True
return False
def solve(a, k):
if dfs(0, 0, a, k):
print "Yes"
else:
print "No"
solve([1, 2, 4, 7], 13)
solve([1, 2, 4, 7], 15)