Submission #569250

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Source Code Expand

#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <algorithm>
#include <sstream>
#include <map>
#include <set>

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<30
#define pb push_back
#define mp make_pair

using namespace std;
typedef long long ll;
typedef pair<int,int> P;

int main() {
	int n;
	cin >> n;

	string s;
	cin >> s;

	if(s.size() % 2 == 1) {
		cout << -1 << endl;
		return 0;
	}

	string a = s.substr(0, s.size()/2);
	string b = s.substr(s.size()/2);


	int ans = 0;
	rep(i, a.size()) {
		if(a[i] == b[i]) {
			continue;
		} else {
			ans++;
		}
	}

	cout << ans << endl;

	return 0;
}

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