/in/foo.c: In function 'main':
/in/foo.c:9:6: error: 'i' undeclared (first use in this function)
  for(i=0;i=<((y1-x1)/2);i++)
      ^
/in/foo.c:9:6: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:9:12: error: expected expression before '<' token
  for(i=0;i=<((y1-x1)/2);i++)
            ^
/in/foo.c:11:7: error: 'j' undeclared (first use in this function)
   for(j=1;j=<((y2-x2)/2;j++)
       ^
/in/foo.c:11:13: error: expected expression before '<' token
   for(j=1;j=<((y2-x2)/2;j++)
             ^
/in/foo.c:18:2: error: expected expression before '}' token
  }
  ^
/in/foo.c:18:2: error: expected expression before '}' token
/in/foo.c:7:9: warning: unused variable 'y2' [-Wunused-variable]
  int y1,y2;
         ^~
/in/foo.c:7:6: warning: unused variable 'y1' [-Wunused-variable]
  int y1,y2;
      ^~
/in/foo.c:6:9: warning: unused variable 'x2' [-Wunused-variable]
  int x1,x2;
         ^~
/in/foo.c:6:6: warning: unused variable 'x1' [-Wunused-variable]
  int x1,x2;
      ^~
/in/foo.c:5:8: warning: unused variable 'm' [-Wunused-variable]
  int n,m;
        ^
/in/foo.c:5:6: warning: unused variable 'n' [-Wunused-variable]
  int n,m;
      ^