Cod sursa(job #1132699)
Utilizator | Data | 3 martie 2014 20:30:04 | |
---|---|---|---|
Problema | Aria | Scor | 0 |
Compilator | fpc | Status | done |
Runda | Arhiva educationala | Marime | 0.45 kb |
program aria;
var f,g:Text;
x,y:array[0..100000] of longint;
b1,b2:array[0..1 shl 23] of char;
i,n,j,k,u,x1,y1,x2,y2:longint;
begin
assign(f,'aria.in');reset(F);settextbuf(f,b1);
assign(g,'aria.out');rewrite(G);settextbuf(g,b2);
readln(f,n);
for i:=1 to n do
readln(f,x[i],y[i]);
x[n+1]:=x[1];
y[n+1]:=y[1];
for i:=1 to n do
k:=k+(x[i]*y[i+1])-(x[i+1]*y[i]);
writeln(g,(k / 2):0:5);
close(F);
close(G);
end.