/in/foo.cc: In function 'int main()':
/in/foo.cc:114:15: warning: 'na' is used uninitialized in this function [-Wuninitialized]
  for(int i=1;i<=na;i++){
              ~^~~~
/in/foo.cc:117:15: warning: 'nb' may be used uninitialized in this function [-Wmaybe-uninitialized]
  for(int i=1;i<=nb;i++){
              ~^~~~
/in/foo.cc:122:15: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  for(int i=1;i<=n;i++){
              ~^~~