a question about standard algorithm

[greghua]

#include <iostream>
#include <string>
#include <functional>

using namespace std;

int count(const string& s, char c)
{
	string::iterator i=find(s.begin(),s.end(),c);
	int n=0;
	while(i!=s.end())
	{
		++n;
		i=find(i+1,s.end(),c);
	}
	return n;
}

void main()
{
	cout<<cout("Abcdiadcsa",'a')<<endl;
}

when compile, compiler says that find is an undeclared identifier.
find is a standard algorithm, should i include any other head file?