Compilare: user.cpp: In function ‘int main()’: user.cpp:141:13: warning: unused variable ‘j’ [-Wunused-variable] long i, j; ^ user.cpp:142:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("logic.in", "r", stdin); ^ user.cpp:143:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("logic.out", "w", stdout); ^ user.cpp:144:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%ld\n", &n); ^ user.cpp:146:24: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(expres[0]); ^ user.cpp:147:24: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(expres[1]); ^ /tmp/ccQNSlHj.o: In function `main': user.cpp:(.text.startup+0x97): warning: the `gets' function is dangerous and should not be used.