HDU 1042 N!

#include <iostream>
#include <cstring>
using namespace std;
int ans[10000],tmp,n,len;
int main()
{
while(~scanf("%d",&n))
{
memset(ans,0,sizeof(ans));
len=ans[1]=1;
for(int i=1;i<=n;i++)
{
tmp=0;
for(int j=1;j<=len;j++)
{
ans[j]=ans[j]*i+tmp;
tmp=ans[j]/10000;
ans[j]%=10000;
}
while(tmp)
{
ans[++len]=tmp%10000;
tmp/=10000;
}
}
printf("%d",ans[len]);
for(int i=len-1;i>0;i--) printf("%04d",ans[i]);
puts("");
}
}