/in/foo.cc: In function 'int sigma(int)':
/in/foo.cc:37:9: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return ans;
         ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:49:25: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
    printf("%d",sigma(m));
                         ^