Compilare: main.c: In function 'main': main.c:66:2: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d %d\n", &n, &m); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:76:4: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%ld", &vec[i][j]); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:88:2: warning: 'sum' is used uninitialized in this function [-Wuninitialized] fprintf(out, "%ld\n", sum); ^~~~~~~~~~~~~~~~~~~~~~~~~~