Compilare: user.cpp: In function ‘int main()’: user.cpp:22:18: warning: unused variable ‘o’ [-Wunused-variable] int a, b, i, o, n, m, op; ^ user.cpp:27:27: 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:33:38: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin,"%d%d%d", &op, &a, &b); ^