Main.c: In function 'main':
Main.c:40:9: error: 'i' undeclared (first use in this function)
   40 |     for(i=0;i<rw;i++){
      |         ^
Main.c:40:9: note: each undeclared identifier is reported only once for each function it appears in
Main.c:24:18: warning: variable 'sz' set but not used [-Wunused-but-set-variable]
   24 |     int rw,rz,sw,sz;
      |                  ^~
Main.c:24:15: warning: unused variable 'sw' [-Wunused-variable]
   24 |     int rw,rz,sw,sz;
      |               ^~