Compilare: main.cpp: In function 'int main()': main.cpp:9:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sum.in", "rt", stdin); ^ main.cpp:11:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("sum.out", "wt", stdout); ^ main.cpp:13:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ main.cpp:22:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&x); ^ main.cpp:18:13: warning: iteration 100003 invokes undefined behavior [-Waggressive-loop-optimizations] if (phi[i]==i) ~~~~~^ main.cpp:17:12: note: within this loop for ( i=2;i<=nmax;i++) ^ main.cpp:15:35: warning: iteration 100004 invokes undefined behavior [-Waggressive-loop-optimizations] for ( i=1;i<=nmax;i++) phi[i]=i; ~~~~~~^~ main.cpp:15:17: note: within this loop for ( i=1;i<=nmax;i++) phi[i]=i; ^