hdu 5597(欧拉，找规律)

#include <iostream>   //打表找规律
#define LL long long
#include <cmath>

using namespace std;

LL c(int a, int b)
{
LL t = 1;

if (a > b - a)
{
a = b - a;
}

for (int i = 1; i <= a; i++)
{
t = t * (b - i + 1) / i;
}

return t;
}

int main()
{
for (int x = 1; x <= 10; x++)
{
double sum = 0;

for (int k = 0; k <= x; k++)
{
// cout << "c " << k << ' ' << 2 * x - k + 1 << ' ' << c(k, 2 * x - k + 1) << endl;
sum += pow(-1.0, k) * pow (2.0, 2 * x - 2 * k) * c(k, 2 * x - k + 1) ;
}

printf("%d %lld\n", x, (LL)sum);
}
}

#include <iostream>
#define LL __int64

using namespace std;

LL euler(LL n)
{
LL res = n, a = n;

for(LL i = 2; i * i <= a; i++)  //没用LL，TLE两发
{
if(a % i == 0)
{
res = res / i * (i - 1);

while (a % i == 0)
{
a /= i;
}
}
}

if (a > 1)
{
res = res / a * (a - 1);
}

return res;
}

int main()
{
LL n, x;
while (~scanf("%I64d%I64d", &n, &x))
{
LL ans = euler(n + x + 1);
printf("%I64d\n", ans);
}

return 0;
}