#include <iostream>
using namespace std;

int main() 
{
	int N;
    char X;
    char Y;

    int fights = 0;

    1 <= N <= 100000;

    for (int i = 0; i < N; i++){
        cin >> X[i];
        cin >> Y[i];

        if (Y[i] != X[i]){
           fights += 1;
        }     
    }
    cout << fights;

    return 0;
}