Compilare: user.cpp: In function ‘int main()’: user.cpp:22:7: warning: unused variable ‘n’ [-Wunused-variable] int n, k, sol = 0; ^ user.cpp:22:10: warning: unused variable ‘k’ [-Wunused-variable] int n, k, sol = 0; ^ user.cpp:20:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grad.in", "r", stdin); ^ user.cpp:21:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grad.out", "w", stdout); ^ user.cpp:23:10: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccxeWqPC.o: In function `main': user.cpp:(.text.startup+0x56): warning: the `gets' function is dangerous and should not be used.