foo.cc: In function 'int main()':
foo.cc:14:2: warning: this 'else' clause does not guard... [-Wmisleading-indentation]
  else
  ^~~~
foo.cc:16:3: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'else'
   while(a<=n)
   ^~~~~
foo.cc:7:13: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int amin=2,n; 
             ^