Compilare: user.cpp: In function ‘int main()’: user.cpp:75:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ai.in","r",stdin); ^ user.cpp:76:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ai.out","w",stdout); ^ user.cpp:77:84: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d%d%d%d%d%d%d%d%d",&N,&T1,&T2,&S1,&S2,&S3,&S4,&R1,&R2,&R3,&R4,&K); ^ user.cpp:79:67: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&val[i].x,&val[i].y),v[val[i].x][val[i].y]=-1; ^