#include "stdio.h"

#include "stdlib.h"

#include "string.h"

#ifndef max

#define max(a, b) ((a) > (b) ? (a) : (b))

#endif

int main() {

int t, m;

scanf("%d %d", &t, &m);

int * dp = (int *)malloc((t + 1) * sizeof(int));

memset(dp, 0, (t + 1) * sizeof(int));

short * time = (short *)malloc(m * sizeof(short));

short * value = (short *)malloc(m * sizeof(short));

for (int i = 0; i < m; i++) {

scanf("%hd %hd", time + i, value + i);

}

for (int i = 0; i < m; i++)

for (int j = time[i]; j <= t; j++)

dp[j] = max(dp[j], dp[j - time[i]] + value[i]);

printf("%d", dp[t]);

free(dp);

free(time);

free(value);

return 0;

}