#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
void FASTCODE() {
std::ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int main() {
FASTCODE();
int n;
cin >> n;
string s;
cin >> s;
string temp = s;
int counter = 0;
for (int i = 0; i < n; i++) {
int fre[243] = { 0 }, arr[10] = { 0 }, r = 0;
//s = temp;
string x=s.substr(i, 3);
sort(x.begin(),x.end());
//cout << x << " ";
for (int j = 0; j < 3; j++) {
fre[x[j]]++;
}
//cout << endl;
for (int k = 48; k <= 122; k++) {
if (fre[char(k)] != 0) {
arr[r] = fre[char(k)];
//cout << fre[char(k)] << " ";
r++;
}
}
//cout << endl;
/*for(int g=0;g<r;g++){
cout << arr[g] << " ";
}*/
//cout << endl;
if (arr[0] == 2 && arr[1] == 1) {
counter++;
}
else if (arr[1] == 2 && arr[0] == 1) {
counter++;
}
else if(arr[0]==3&& arr[1]==0){
counter++;
}
}
cout << counter;
return 0;
}
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