// editor4
#include <stdio.h>

int main() {
    int m, n;
    scanf("%d %d", &m, &n);
    int prices[10][10];
    int total_cost = 0;
    
    for (int i = 0; i < m; i++) {
        for (int j = 0; j < n; j++) {
            scanf("%d", &prices[i][j]);
            if (prices[i][j] < 0) {
                printf("Invalid input\n")
                return 0;
            }
            total_cost += prices[i][j];
        }
    }
    
    printf("%d\n", total_cost);
    
    return 0;
}