code:

// C++ program to approximate number of people in Birthday Paradox 
// problem
#include <cmath>
#include <iostream>
using namespace std;
 
// Returns approximate number of people for a given probability
int find(double p)
{
    return ceil(sqrt(2*365*log(1/(1-p))));
}
 
int main()
{
   cout << find(0.70);
}