#include <bits/stdc++.h> using namespace std; template<class T> bool chmax(T &a, const T &x) { return x > a ? a = x, true : false; } int main() { int N, K; long long P; cin >> N >> P >> K; constexpr long long inf = 1e18; vector<long long> dp(K+1, -inf); dp[0] = P; while (N--) { int T, B; cin >> T >> B; vector<long long> _dp = dp; for (int k = 1; k <= K; ++k) { chmax(_dp[k], dp[k-1] * T + B); if (_dp[k] > inf) { cout << -1 << endl; return 0; } } dp = move(_dp); } cout << dp[K] << endl; return 0; }