Compilare: main.cpp: In function 'void build_pcts(std::vector<pct>&, std::vector<pct>&, int, int, int)': main.cpp:41:11: warning: suggest explicit braces to avoid ambiguous 'else' [-Wparentheses] if(poz1!=i and poz2!=i) ^ main.cpp: In function 'long long int area(std::vector<pct>&)': main.cpp:85:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v.size();i++) ~^~~~~~~~~ main.cpp: In function 'bool ok(std::vector<pct>&)': main.cpp:103:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i==v.size()-1) ~^~~~~~~~~~~~ main.cpp:106:11: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k+1!=v.size() or cross(v[hull[k-1]],v[hull[k]],v[0])<0) ~~~^~~~~~~~~~ main.cpp:108:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v.size();i++) ~^~~~~~~~~ main.cpp:110:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v.size();i++) ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:141:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ~^~~~~~~~~