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Cod sursa(job #265251)
#include <stdio.h>
#include <math.h>
#define maxn 10010
#define maxnr 1000010
using namespace std;
long n, i, j, k, m, l, ndp, r, nr, nrb, pr, sum, d;
long long sol;
long v[maxnr], dp[maxnr], f[maxnr];
int main()
{
freopen("pairs.in", "r", stdin);
freopen("pairs.out", "w", stdout);
scanf("%d\n", &n);
sol=0;
for(i=1; i<=n; i++)
{
sum=0;
scanf("%d", &v[i]);
d=1;
nr=0;
r = (long)sqrt(v[i]);
while(v[i]>1 && d<=r)
{
d++;
if(v[i] % d==0)
{
nr++;
dp[nr]=d;
while(v[i] % d == 0)
{
v[i]/=d;
}
}
}
if(v[i]>1)
{
nr++;
dp[nr]=v[i];
}
for(j=1; j<(1<<nr); j++)
{
nrb=0;
pr=1;
for(l=0; l<nr; l++)
{
if( (1<<l) & j)
{
nrb++;
pr*=dp[l+1];
}
}
if(nrb%2==0)
{
sum-=f[pr];
}
else
{
sum+=f[pr];
}
f[pr]++;
}
sol+=i-sum-1;
}
printf("%lld\n", sol);
return 0;
}