Compilare: user.cpp: In function ‘int main()’: user.cpp:24:6: warning: unused variable ‘sum’ [-Wunused-variable] int sum = 0; ^ user.cpp:18:29: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d%d", &N, &M); ^ user.cpp:22:30: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(a[i] + 1, N + 3, fin); ^