Submission #1292612

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Source Code Expand

#include<iostream>
#include<algorithm>
#include<vector>
#include<math.h>
#include<string>
#include<limits.h>
#define ll long long
#define vl vector<ll> 
#define vb vector<bool> 
#define vvl vector<vector<ll> > 
#define vvb vector<vector<ll> > 
#define rep(i,n) for(int i=0;i<n;i++)
#define nrep(i,a,b) for(int i=a;i<b;i++)
#define mrep(i,a) for(int i=a;i>=0;i++)
#define mmrep(i,a) for(int i=a;i>0;i++)
#define INF 1123456789012345
using namespace std;

ll no() {
	cout << -1 << endl;
	exit(0);
}

int main() {
	ll n; cin >> n;
	string s; cin >> s;
	if ((n - 1) % 2) no();
	if (s[n / 2] != 'b') no();
	ll r = (n - 1) / 2 + 1;
	ll l = (n - 1) / 2 - 1;
	string r_s = "cab";
	string l_s = "acb";
	ll r_index = 0;
	ll l_index = 0;
	while (l > 0) {
		if (!(r_s[r_index % 3] == s[r] && s[l] == l_s[r_index % 3])) no();
		l--; r++;
		r_index++;
	}cout << (n - 1) / 2 << endl;
	return 0;
}

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