/*
On the copybookProgram..
UseC LanguageWrite always wa The most efficient exchange for each selection
*/
# Include < Iostream >
# Include < Fstream >
# Include < Vector >
# Include < Algorithm >
Using Namespace STD;
Struct Mouse
{
Double J, F;
Double Shouyi;
};
Bool Comp ( Const Mouse & D1, Const Mouse & D2 ){
If (D1.shouyi ! = D2.shouyi)
Return D2.shouyi < D1.shouyi;
Return D2.f > D1.f;
}
Int Main (){
// Ifstream CIN ("2109.txt ");
Vector < Mouse > V;
Mouse mouse;
Int M, n, I;
Cout. Precision ( 3 ); // Decimal places
Double SUM;
While (CIN > M > N ){
If (M = - 1 && N = - 1 )
Break ;
V. Clear ();
Sum = 0.0 ;
For (I = 0 ; I < N; ++ I ){
CIN > Mouse. j > Mouse. F;
Mouse. Shouyi = Mouse. j / Mouse. F;
V. push_back (Mouse );
}
Sort (V. Begin (), V. End (), comp );
For (I = 0 ; I < V. Size (); I ++ ){
If (M > = V [I]. f ){
Sum + = V [I]. J;
M -= ( Int ) V [I]. F;
} Else {
Sum + = M * V [I]. Shouyi;
Break ;
}
}
Cout < Fixed < Sum < Endl;
}
Return 0 ;
}