Compilare: main.cpp: In function 'int main()': main.cpp:49:51: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("beyond_the_wall.in", "r", stdin); ^ main.cpp:50:53: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("beyond_the_wall.out", "w", stdout); ^ main.cpp: At global scope: main.cpp:18:22: warning: 'Y' defined but not used [-Wunused-variable] static int X[1 + N], Y[1 + N]; ^ main.cpp:18:12: warning: 'X' defined but not used [-Wunused-variable] static int X[1 + N], Y[1 + N]; ^