Compilare: main.c: In function 'main': main.c:21:13: warning: implicit declaration of function 'isdigit' [-Wimplicit-function-declaration] if(!isdigit(a+48) || !isdigit(b+48)){ ^~~~~~~ main.c:11:1: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lld", &T); ^~~~~~~~~~~~~~~~~~~~~~~~~ main.c:15:5: warning: ignoring return value of 'fscanf', declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lld", &N); ^~~~~~~~~~~~~~~~~~~~~~~~~