/in/foo.c: In function 'main':
/in/foo.c:6:17: error: 'x1' undeclared (first use in this function)
  scanf("%d %d",&x1,&x2);
                 ^~
/in/foo.c:6:17: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:21: error: 'x2' undeclared (first use in this function)
  scanf("%d %d",&x1,&x2);
                     ^~
/in/foo.c:7:16: error: stray '\' in program
  printf("y1=%d"\n,x1+x2);
                ^
/in/foo.c:7:17: error: expected ')' before 'n'
  printf("y1=%d"\n,x1+x2);
                 ^
/in/foo.c:7:14: warning: format '%d' expects a matching 'int' argument [-Wformat=]
  printf("y1=%d"\n,x1+x2);
              ^
/in/foo.c:8:16: error: stray '\' in program
  printf("y2=%d"\n,x1*x2);
                ^
/in/foo.c:8:17: error: expected ')' before 'n'
  printf("y2=%d"\n,x1*x2);
                 ^
/in/foo.c:8:14: warning: format '%d' expects a matching 'int' argument [-Wformat=]
  printf("y2=%d"\n,x1*x2);
              ^
/in/foo.c:9:16: error: stray '\' in program
  printf("y3=%d"\n,x1/x2);
                ^
/in/foo.c:9:17: error: expected ')' before 'n'
  printf("y3=%d"\n,x1/x2);
                 ^
/in/foo.c:9:14: warning: format '%d' expects a matching 'int' argument [-Wformat=]
  printf("y3=%d"\n,x1/x2);
              ^