/in/foo.c: In function 'main':
/in/foo.c:13:12: warning: array subscript has type 'char' [-Wchar-subscripts]
         tab[i] = tab[i+1];
            ^
/in/foo.c:18:12: warning: array subscript has type 'char' [-Wchar-subscripts]
         tab[i] = tab[i+2];
            ^
/in/foo.c:23:20: warning: array subscript has type 'char' [-Wchar-subscripts]
         sum += (tab[i] - '0') * i;
                    ^