#include #include using namespace std;int main(){ const long N = 600000; // Length of tuples x and y const long S = 10; // Sparseness factor map x, y; for (long k = 0; 3 * k * S < N; ++k) x[3 * k * S] = 1.0; for (long k = 0; 5 * k * S < N; ++k) y[5 * k * S] = 1.0; double sum; map::iterator ix, iy; for (sum = 0.0, ix = x.begin(); ix != x.end(); ++ix) { long i = ix->first; iy = y.find(i); if (iy != y.end()) sum += ix->second * iy->second; } cout << sum << endl; return 0;} /* 4000 */