Compilare: user.cpp: In function ‘int main()’: user.cpp:21:70: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sortnet.in","r",stdin),freopen("sortnet.out","w",stdout); ^ user.cpp:21:70: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] user.cpp:22:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:25:74: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf(" <%d ,%d >",&lo,&hi),--lo,--hi,a[i][lo].u=hi,a[i][hi].v=lo; ^