Compilare: user.cpp: In function ‘int main()’: user.cpp:17:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dif2.in","r",stdin); ^ user.cpp:18:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dif2.out","w",stdout); ^ user.cpp:20:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld",&c); ^ user.cpp:22:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld",&n); ^ user.cpp:24:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&v[i]); ^ user.cpp:28:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld%lld%lld",&n,&p1,&p2); ^ user.cpp:30:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&v[i]); ^ user.cpp:51:7: warning: ‘val1’ may be used uninitialized in this function [-Wmaybe-uninitialized] printf("%lld\n",val1-val2); ~~~~~~^~~~~~~~~~~~~~~~~~~~ user.cpp:51:7: warning: ‘val2’ may be used uninitialized in this function [-Wmaybe-uninitialized]