#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; const int inf = 1e9; const int maxh = 1e5; pair< long long, long long > ct[maxh + 5]; int main() { long long n, m; int h; cin >> n >> m >> h; //scanf("%I64d%I64d%d", &n, &m, &h); //scanf("%lld%lld%d", &n, &m, &h); for (int i = 0; i < h; ++i) //scanf("%I64d%I64d", &ct[i].second, &ct[i].first); //scanf("%lld%lld", &ct[i].second, &ct[i].first); cin >> ct[i].second >> ct[i].first; sort(ct, ct + h); long long cnt = 0; long long ans = 0; for (int i = 0; i < h; ++i) { if (cnt + ct[i].second < n * m) ans += ct[i].second * ct[i].first, cnt += ct[i].second; else { ans += (n * m - cnt) * ct[i].first; cout << ans << "\n"; return 0; } } cout << "Impossible\n"; return 0; }