/in/foo.cc: In function 'bool check(int)':
/in/foo.cc:7:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   if(k==2)
     ^
/in/foo.cc:10:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses]
   if(b[k]+b[k-1]+b[k-2]==a[k-1])
     ^