1276

#include <iostream>#include <cstring>using namespace std;int cash, N, n[10], D[10], ans;short used[100001];int main(){while(cin >> cash >> N){for(int i = 0; i < N; ++i){cin >> n[i] >> D[i];}if(N && cash){memset(used, -1, sizeof(used));used[0] = 0;for(int i = 0; i < N && -1 == used[cash]; ++i){if(n[i]){for(int j = D[i]; j <= cash; ++j){if(used[j] != -1){used[j] = 0;}else{used[j] = -1;if(used[j - D[i]] != -1 && used[j - D[i]] < n[i]){used[j] = used[j - D[i]] + 1;}}}}}for(ans = cash; -1 == used[ans]; --ans);cout << ans << endl;}else{cout << 0 << endl;}}return 0;}