#include<stdio.h>

int main()

{

int i,num,n,total;

double ave;

while(scanf("%d",&n)!=EOF)

{

total=0;

num=0;

for(i=1;i<=n ;i++)

{scanf("%d",&num);

total=total+num;

}

ave= (double)total/n;

if(ave<59)

printf("yes\n");

else

printf("no\n");

}

return 0;

}