Compilare: user.cpp: In function ‘int main()’: user.cpp:21:9: warning: unused variable ‘start’ [-Wunused-variable] int start; ^ user.cpp:20:32: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d %d", &n, &m); ^ user.cpp:26:41: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d", &mat[i][j]); ^