Compilare: user.cpp: In function ‘int main()’: user.cpp:8:26: warning: unused variable ‘i’ [-Wunused-variable] int n,x,y,z,t,s=0,su=0,i; ^ user.cpp:6:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("koba.in","r",stdin); ^ user.cpp:7:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("koba.out","w",stdout); ^ user.cpp:9:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d",&n,&x,&y,&z); ^