#15357: __py
sbg_hvk103019
(Pytest931)
import sys
for i in sys.stdin:
a=[int(x) for x in i.split()]
a1=a[1:]
a2=a[0]
score=0
for j in a1:
score+=j
if (score/a2)>59:
print('no')
else:
print('yes')