Compilare: user.cpp: In function ‘int main()’: user.cpp:18:9: warning: unused variable ‘a’ [-Wunused-variable] int a, b, c; ^ user.cpp:18:12: warning: unused variable ‘b’ [-Wunused-variable] int a, b, c; ^ user.cpp:18:15: warning: unused variable ‘c’ [-Wunused-variable] int a, b, c; ^ user.cpp:17:24: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d", &n); ^ user.cpp:20:70: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fi,"%d%d%d%d", &v[i][0], &v[i][1], &v[i][2], &v[i][3]); ^