基因相关性

#include <iostream>
#include <cstring>
using namespace std;

int main()
{	
	char a[100], b[100];
	double x, len, mean = 0;
	cin >> x >> a >> b;
	len = strlen(a);
	for (int i = 0; i < len; i++)
	{
		if (a[i] == b[i])
			mean++;
	}
	double y = mean / len * 1.0;
	if (y >= x)
	{
		cout << "yes" << endl;
	}
	else
	{
		cout << "no" << endl;
	}
	return 0;
}这哪错了啊？