求平均数 用free pascal

var n:longint;
m,a,r:real;
begin
n:=0;m:=0;
while not eoln do {eoln 代表行结束(end of line);eof 代表文件结束(end of file)}
begin
inc(n);
read(a);
m:=m+a;
end;
r:=m / n;
writeln(r:0:4);
end.