Compilare: main.cpp: In function 'int main(int, const char**)': main.cpp:43:6: warning: variable 'last_a' set but not used [-Wunused-but-set-variable] int last_a = v[0].first; ^~~~~~ main.cpp:54:44: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized] } else if(v[i].first == a && v[i].second == b) { main.cpp:27:6: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized] int a, b, val, x, y; ^