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OI-codes/AcWing/772/772.cpp

34 lines
649 B
C++

#include <bits/stdc++.h>
using namespace std;
int main() {
string s;
vector<char> ans;
int a = -1;
char c = 'a';
cin >> s;
map<char, int> m, m1;
for (int i = 0; i < s.size(); i++) {
m[s[i]]++;
if (!m1.count(s[i])) m1[s[i]] = i;
}
for (char i = 'a'; i <= 'z'; i++) {
if (m[i] == 1) {
ans.push_back(i);
}
}
if (ans.empty()) {
cout << "no" << endl;
} else {
for (char i : ans) {
if (a == -1 || m1[i] < a) {
a = m1[i];
c = i;
}
}
cout << c << endl;
}
return 0;
}