Compilare: main.cpp: In function 'int main()': main.cpp:6:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("hacker3.in", "r", stdin); ^ main.cpp:7:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("hacker3.out", "w", stdout); ^ main.cpp:10:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d\n", &n); ^ main.cpp:13:55: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d\n", &cost[i].first, &cost[i].second); ^