用vf编程!求级数s=1+1/2-1/3+1/4~

clear
s=1
input "请输入n的值：" to n
for i=2 to n
k=(-1)^i
m=k/i
s=s+m
endfor
"s=1+1/2-1/3+1/4+...+1/n",s