BZOJ 1968: [Ahoi2005]COMMON 约数研究

我只能说这是一道灵性的傻逼题
扫一遍，每个数对约数总数的贡献是n/i
就这样。。。

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#include<cstdio>#include<cstring>#include<algorithm>#define g getchar()#define ll long long#define inf 0x3f3f3f3fusing namespace std;inline ll read(){    ll x=0,f=1;char ch=g;    for(;ch<'0'||ch>'9';ch=g)if(ch=='-')f=-1;    for(;ch>='0'&&ch<='9';ch=g)x=x*10+ch-'0';    return x*f;}inline void out(ll x){    int a[25],wei=0;    if(x<0)putchar('-'),x=-x;    for(;x;x/=10)a[++wei]=x%10;    if(wei==0){puts("0");return;}    for(int j=wei;j>=1;--j)putchar('0'+a[j]);    putchar('\n');}int n,ans;int main(){//  freopen("","r",stdin);//  freopen("","w",stdout);    int n=read();    for(int i=1;i<=n;++i)    ans+=n/i;out(ans);    return 0;}