
#include <stdio.h>
int ff(int n)
{
int i = 2;
while (i < n)
{
if (n % i == 0)
{
n = 0;
break;
}
else i++;
}
return n;
}
int main()
{
int n, m, i;
int sum;
scanf_s("%d %d",&m,&n);
if (m > n) {
for (sum = 0, i = n; i <= m; i++)
{
sum = sum + ff(i);
}
}
else if (m < n) {
for (sum = 0, i = m; i <= n; i++)
{
sum = sum + ff(i);
}
}
else sum = ff(m);
printf("%d\n",sum);
return 0;
}

