Compilare: main.cpp: In function 'int main()': main.cpp:123:44: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nambartiori.in" , "r" , stdin); ^ main.cpp:124:46: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nambartiori.out" , "w" , stdout); ^ main.cpp: In function 'void get_ll(ll&)': main.cpp:16:35: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buffer , sz , 1 , stdin); ^ main.cpp: In function 'int main()': main.cpp:128:15: warning: iteration 31621 invokes undefined behavior [-Waggressive-loop-optimizations] if(p[i] == 0) ~~~^ main.cpp:127:19: note: within this loop for(i = 2 ; i <= lim ; i ++) ~~^~~~~~ main.cpp:78:19: warning: 'last' may be used uninitialized in this function [-Wmaybe-uninitialized] return last + 1; ^ main.cpp:62:24: note: 'last' was declared here ll st , dr , med , last , sum; ^~~~ main.cpp:119:15: warning: 'last' may be used uninitialized in this function [-Wmaybe-uninitialized] printf("%lld %lld\n" , first , 2 * first); ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:96:24: note: 'last' was declared here ll st , dr , med , last; ^~~~