#include <iostream.h> #include <stdlib.h> #include <stdio.h> #include <fstream.h> ifstream f("mouse.in"); #define cin f int comp(const void *m,const void *n) { return ((int *)n)[0]/((int *)n)[1]-((int *)m)[0]/((int *)m)[1]; }      int main() {     int m,n;     int a[1000][2];     int i,j;     while(cin>>m>>n)     {         if (m==-1 && n==-1)         return 0;         for(i=0;i<n;i++)         cin>>a[i][0]>>a[i][1];         qsort(a,n,2*sizeof(int),comp);         float k=(float)m;         i=0;         float Msum=0.0;         //for(i=0;i<n;i++)         //cout<<a[i][0]<<" "<<a[i][1]<<endl;         //i=0;         while(1)         {             if(k-(float)a[i][1]>0.00001)             {             Msum=Msum+a[i][0];             //i++;             k=k-(float)a[i][1];             i++;             }                 else             {                 Msum=Msum+k*((float)((float)a[i][0]/a[i][1]));                 break;             }         }         //cout<<Msum<<endl;             printf("%0.3f\n",Msum);                                      /*r(i=0;i<n;i++)         for(j=0;j<n-1-i;j++)         if (a[j][0]/a[j][1]-a[j+1][0]/a[j+1][1]>0)         {             int a1=a[j][0];             int a2=a[j][1];             a[j][0]=a[j+1][0];             a[j][1]=a[j+1][1];             a[j+1][0]=a1;             a[j+1][1]=a2;         }         //for(i=0;i<n;i++)         //cout<<a[i][0]<<" "<<a[i][1]<<endl;         float Msum=0.0;         float yu=(float)m;         for(i=n-1;i>=0;i--)         {             if(yu-a[i][1]>0)             {             Msum=Msum+a[i][0];             yu=yu-a[i][1];             }                 else             {                 Msum=Msum+yu*((float)(a[i][0]/a[i][1]));                 break;             }         }         cout<<yu<<endl;             } */           // for(i=0;i<n;i++)         //cout<<a[i][0]<<" "<<a[i][1]<<endl;     }    }       

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