/in/foo.c: In function 'main':
/in/foo.c:70:21: error: 'n1' undeclared (first use in this function)
  scanf("%d %d",&x1,&n1);
                     ^~
/in/foo.c:70:21: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:71:21: error: 'n2' undeclared (first use in this function)
  scanf("%d %d",&x2,&n2);
                     ^~
/in/foo.c:68:6: warning: unused variable 'nb' [-Wunused-variable]
  int nb=1;
      ^~
/in/foo.c:67:6: warning: unused variable 'na' [-Wunused-variable]
  int na=1;
      ^~