2.2

#include <stdio.h>
#include <stdlib.h>

long long f(int n)
{
    int*a=calloc(n+1,sizeof(int));
    long long s=0;
    int d=2;
    int k=0;
    long long p=d;
    while(n/p!=0)
    {
        k+=n/p;
        p*=d;
    }
    s=s+k*d;
    long long x=d;
    while(x<=n)
    {
        a[x]=1;
        x+=d;
    }
    for(d=3; d<=n; d+=2)
    {
        if(a[d]==0)
        {
            k=0;
            p=d;
            while(n/p)
            {
                k+=n/p;
                p*=d;
            }
            s=s+k*d;
            if(d*d<n)
            {
                x=(long long)d*d;
                while(x<=n)
                {
                    a[x]=1;
                    x+=d;
                }
            }
        }
    }
    free(a);
    return s;
}

int main()
{
    int n;
    scanf("%d",&n);
    printf("%lld",f(n));
    return 0;
}