Compilare: main.cpp: In function 'int main()': main.cpp:37:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("trapezoid.in", "r", stdin); ^ main.cpp:38:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("trapezoid.out", "w", stdout); ^ main.cpp:40:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &n); ^ main.cpp:42:63: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d%d%d", &a[i].x1, &a[i].x2, &a[i].y1, &a[i].y2); ^