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Cod sursa(job #591878)
#include <algorithm>
#include <stdio.h>
#define MAX 1000010
#define ll long long
using namespace std;
int dp[MAX], prim[MAX];
int n, m;
ll sol;
int main()
{
freopen("mins.in", "r", stdin);
freopen("mins.out", "w", stdout);
scanf("%d %d", &n, &m);
n--, m--;
if (n > m)
swap(n, m);
for (int i = 2; i <= n; i++)
{
if (!prim[i])
{
for (int j = i; j <= n; j += i)
{
prim[j] = 1;
dp[j]++;
}
for (ll j = i * i; j <= n; j += (ll) i * i)
dp[j] = -LONG_MAX;
}
if (dp[i] > 0)
{
int im = m / i;
if (!(dp[i] & 1))
im *= -im;
sol += (im * (n / i));
}
}
printf("%lld\n", (ll) n * m - sol);
fclose(stdin);
fclose(stdout);
return 0;
}