#include <iostream>
#include <vector>
#include <string>
#include <unordered_map>

using namespace std;

int findShortestTime(const string& S, const string& T) {
    int n = S.length();
    int m = T.length();
    unordered_map<char, vector<int>> charPositions;
    for (int i = 0; i < n; i++) {
        charPositions[S[i]].push_back(i);
    }
    int currentPos = 0;
    int time = 0;
    for (int i = 0; i < m; i++) {
        char targetChar = T[i];
        if (charPositions.find(targetChar) == charPositions.end()) {
            return -1;
        }
        vector<int>& positions = charPositions[targetChar];
        int targetPos = -1;
        int minDistance = n + 1;
        for (int pos : positions) {
            int distance = abs(pos - currentPos);
            if (distance < minDistance) {
                minDistance = distance;
                targetPos = pos;
            }
        }
        if (targetPos == -1) {
            return -1;
        }
        time += minDistance;
        currentPos = targetPos;
    }
    return time;
}

int main() {
    int n, m;
    cin >> n >> m;
    string S, T;
    cin >> S >> T;
    cout << findShortestTime(S, T) << endl;
    return 0;
}

In file included from /usr/include/c++/4.8/unordered_map:35:0,
                 from answer.code:4:
/usr/include/c++/4.8/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support is currently experimental, and must be enabled with the -std=c++11 or -std=gnu++11 compiler options.
 #error This file requires compiler and library support for the \
  ^
answer.code: In function 'int findShortestTime(const string&, const string&...