Compilare: main.cpp: In function 'int main()': main.cpp:16:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 2;i <= n;i++) ~~^~~~ main.cpp:19:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1;i < n;i++) ~~^~~ main.cpp:21:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i + i;j < n;j++) ~~^~~ main.cpp:9:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nrecou.in","r",stdin); ^ main.cpp:10:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("nrecou.out","w",stdout); ^ main.cpp:12:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%lld",&n); ^