Compilare: user.cpp:1:2: warning: #import is a deprecated GCC extension [-Wdeprecated] #import<fstream> ^~~~~~ user.cpp:2:33: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] std::ifstream f("aria.in");main(){long double N,a,b,x,y,X,Y,S=0;f>>N>>a>>b;x=a;for(y=b;--N;S+=x*Y-X*y,x=X,y=Y)f>>X>>Y;S+=x*b-a*y;fprintf(fopen("aria.out","w"),"%.5Lf",S/2);} ^