/in/foo.cc: In function 'int main()':
/in/foo.cc:33:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &length);
                         ^
/in/foo.cc:34:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%s", str);
                     ^