var sum = 0
for(var i = 1 i <= 20 i++){
function factorial(i){
if(i == 1){
return 1
}
return factorial ( i - 1 ) * i
}
var ret=factorial(i)
sum += ret
}
alert(sum)
factor(3)function factor(n){
var x = n.toFixed()
if(x==1||x==0){
return 1
}else if(x>0){
return x*a(x-1)
}else{
return -1
}
}
