/in/foo.c: In function 'main':
/in/foo.c:13:14: error: 'j' undeclared (first use in this function)
  for(int i=0;j<i;j++)
              ^
/in/foo.c:13:14: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:21:2: warning: implicit declaration of function 'printfz' [-Wimplicit-function-declaration]
  printfz("%d",Sn);
  ^~~~~~~
/in/foo.c:23:2: error: 'renturn' undeclared (first use in this function)
  renturn 0;
  ^~~~~~~
/in/foo.c:23:10: error: expected ';' before numeric constant
  renturn 0;
          ^