#include <stdio.h>
int main() {
int n = 0;
int m = 0;
scanf("%d %d", &n, &m);
int sum = 0;
int i = 0;
int arr[10][10] = {0};
for (i = 0; i < n; i++) {
int j = 0;
for (j = 0; j < m; j++) {
scanf("%d", &arr[i][j]);
if (arr[i][j] >= 0) {
sum += arr[i][j];
}
}
}
printf("%d\n", sum);
return 0;
}