#include <stdio.h>

int weight[1010];
double time[1010];

int soucetVah(int a, int b)
{
    int min, max;
    int i;
    int soucet;

    min = (a < b) ? a : b;
    max = (a < b) ? b : a;
    soucet = 0;
    for (i = min; i <= max; i++) {
	soucet += weight[i];
    }
    return(soucet);
}

double maximumCasu(int a, int b)
{
    int min, max, i;
    double maximum;

    min = (a < b) ? a : b;
    max = (a < b) ? b : a;
    maximum = time[min];
    for (i = min+1; i <= max; i++) {
	maximum = (maximum > time[i]) ? maximum : time[i];
    }
    return(maximum);
}

void bridge(int load, int length, int cars)
{
    int i, j;
    struct {
        int weight;
        float time;
    } table[1010][1010];
    float opts[1010];

    for (i = 0; i < cars; i++) {
	int speed;
	scanf("%d %d", &weight[i], &speed);
	time[i] = length * 60 / speed;
    }

    for (i = 0; i < cars; i++) {
        opts[i] = 1e10;
        for (j = 0; j <= i; j++) {
	    int w;
	    w = soucetVah(i, j);
	    if (w > load) continue;
	    table[i][j].weight = w;
	    table[i][j].time = maximumCasu(i, j);
	    if (j > 0 && i > 0) table[i][j].time += opts[j-1];
	    opts[i] = (opts[i] <= table[i][j].time) ? opts[i] : table[i][j].time;
/*	    printf(" [%d,%d](%d %.2f)", i, j,
	           table[i][j].weight, table[i][j].time); */
	}
/*	printf(" opt: %.2f\n", opts[i]); */
    }
    printf("%.1f\n", opts[cars-1]);
}

int main(void)
{
    int load, length, cars;
    
    do {
	scanf("%d %d %d", &load, &length, &cars);
	if (load == 0 && length == 0 && cars == 0) break;
	bridge(load, length, cars);
    } while (1);
    return(0);
}