Cod sursa(job #948055)
Utilizator | Data | 9 mai 2013 12:36:40 | |
---|---|---|---|
Problema | Aria | Scor | 0 |
Compilator | fpc | Status | done |
Runda | Arhiva educationala | Marime | 0.49 kb |
program aria;
var n,i:longint;
x,y,x1,y1,a,b,s:extended;
buf:array[1..100000]of byte;
begin
assign(input,'aria.in');
reset(input);
settextbuf(input,buf);
assign(output,'aria.out');
rewrite(output);
readln(n);
readln(a,b);
x1:=a;y1:=b;
for i:=2 to n do
begin
readln(x,y);
s:=s+((y+y1)*(x-x1)/2);
x1:=x;y1:=x;
end;
x:=a;y:=b;
s:=s+((y+y1)*(x-x1)/2);
s:=abs(s);
writeln(s:0:5);
close(input);close(output);
end.