Compilare: user.cpp: In function ‘int main()’: user.cpp:22:10: warning: statement has no effect [-Wunused-value] for(i-1; i<=n; i++){ ^ user.cpp:17:16: warning: unused variable ‘f2’ [-Wunused-variable] FILE *f1, *f2; ^ user.cpp:19:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.out", "w", stdout); ^ user.cpp:21:43: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f1, "%d%d%d%d", &n, &m, &x, &y); ^ user.cpp:27:35: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f1, "%d%d", &j, &k); ^ user.cpp:22:5: warning: ‘i’ may be used uninitialized in this function [-Wmaybe-uninitialized] for(i-1; i<=n; i++){ ^