/in/foo.c:1:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main() { printf("NIE");}
 ^~~~
/in/foo.c: In function 'main':
/in/foo.c:1:10: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
 main() { printf("NIE");}
          ^~~~~~
/in/foo.c:1:10: warning: incompatible implicit declaration of built-in function 'printf'
/in/foo.c:1:10: note: include '<stdio.h>' or provide a declaration of 'printf'