#include < iostream >
using   namespace  std;

int  Max,s,n;
double  w[ 1010 ],c[ 1010 ];
double  f[ 1010 ];
int  main()
{
    scanf( " %d%d%d " , & Max, & s, & n);
    w[ 0 ] = c[ 0 ] = f[ 0 ] = 0.0 ;
     for ( int  i = 1 ;i <= n; ++ i){
        scanf( " %lf%lf " , & w[i], & c[i]);
        f[i] = f[i - 1 ] + s / c[i];
        w[i] += w[i - 1 ];
         double  Min = c[i];
         for ( int  j = i - 1 ;j >= 1 ; -- j)
             if (w[i] - w[j - 1 ] <= ( double )Max){
                 if (Min > c[j])
                    Min = c[j];
                 if (f[i] > f[j - 1 ] + s / Min)
                    f[i] = f[j - 1 ] + s / Min;
            }
             else   break ;
    }
    f[n] = f[n] * 60.0 ;
    printf( " %0.1lf\n " ,f[n]);
     return   0 ;
}