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

using lint = long long;
constexpr lint INF = 1LL << 60;

const std::string JOI = "JOI$";

void solve() {
    int n, k;
    std::cin >> n >> k;

    std::vector<std::pair<std::string, lint>> ps(n);
    for (auto& p : ps) {
        std::cin >> p.first >> p.second;
    }

    std::vector<lint> dp(k * 3 + 1, INF);
    dp[0] = 0;
    for (int l = 0; l < k * 3; ++l) {
        for (const auto& p : ps) {
            int r = l;
            for (char c : p.first) {
                if (c == JOI[r / k]) ++r;
            }

            if (r > l) dp[r] = std::min(dp[r], dp[l] + p.second);
        }
    }

    auto ans = dp.back();
    std::cout << (ans == INF ? -1 : ans) << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}