Compilare: user.cpp: In function ‘int main()’: user.cpp:63:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while ( i < slopes.size() ) { ^ user.cpp:65:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while ( j < slopes.size() && slopes[i].a * slopes[j].b == slopes[j].a * slopes[i].b ) { ^ user.cpp:31:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.in", "r", stdin); ^ user.cpp:32:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trapez.out", "w", stdout); ^ user.cpp:34:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d ", &n); ^ user.cpp:37:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d ", &p[i].x, &p[i].y); ^