/in/foo.c: In function 'main':
/in/foo.c:7:12: error: 'n' undeclared (first use in this function)
  for(i=0;i<n;i++)
            ^
/in/foo.c:7:12: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:8:15: error: 'm' undeclared (first use in this function)
     for(j=0;j<m;j++)
               ^