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Cod sursa(job #635047)
#include <fstream>
#include <algorithm>
using namespace std;
#define unusable -100000
int n, m;
int d[1000001];
long long sol;
int main()
{
int i, j, minim = 0;
ifstream f("mins.in");
ofstream g("mins.out");
f >> n >> m;
--n; --m;
minim = min(n, m);
for(i = 2; i <= minim; ++i)
if(d[i] == 0)
{
for(j = i * i; j <= minim; j += i * i)
d[j] = unusable;
for(j = i; j <= minim; j += i)
++d[j];
}
for (i = 2; i <= minim; i ++)
if (d[i] > 0)
{
if (d[i] & 1)
sol -= (long long)(n / i) * (m / i);
else
sol += (long long)(n / i) * (m / i);
}
g << sol + n * m << '\n';
g.close();
return 0;
}