Compilare: user.cpp: In function ‘int main()’: user.cpp:38:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, n, m, op, a, b, ta, tb, cost=0, lg=0; ^ user.cpp:38:21: warning: unused variable ‘op’ [-Wunused-variable] int i, j, n, m, op, a, b, ta, tb, cost=0, lg=0; ^ user.cpp:38:25: warning: unused variable ‘a’ [-Wunused-variable] int i, j, n, m, op, a, b, ta, tb, cost=0, lg=0; ^ user.cpp:38:28: warning: unused variable ‘b’ [-Wunused-variable] int i, j, n, m, op, a, b, ta, tb, cost=0, lg=0; ^ user.cpp:37:34: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buff, 1, 200000, stdin); ^ user.cpp: In function ‘void read(int&)’: user.cpp:29:136: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] while(buff[pos] < '0' || buff[pos] > '9'){if(buff[pos]== '-' )semn = -1; if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;} ^ user.cpp:31:139: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] while('0' <= buff[pos] && buff[pos] <= '9') {nr = nr * 10 + buff[pos] - '0';if(++pos == 200000) fread(buff, 1, 200000, stdin), pos = 0;} ^