Compilare: user.cpp: In function ‘int main()’: user.cpp:43:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 1; j <= strlen(S + 1); j++) ^ user.cpp:39:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &N); ^ user.cpp:42:24: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(S + 1); ^ /tmp/ccTBBqT4.o: In function `main': user.cpp:(.text.startup+0x4c): warning: the `gets' function is dangerous and should not be used.