#include <stdio.h>

int main() {
    double a[5][3], mult = 1, b;
    scanf("%lf", &b);
    
    for (int i = 0; i < 5; ++i) {
        for (int j = 0; j < 3; ++j) {
            scanf("%lf", &a[i][j]);
        }
    }
    
    for (int i = 0; i < 5; ++i) {
        for (int j = 0; j < 3; ++j) {
            if (a[i][j] < b) {
                mult *= a[i][j];
            }
        }
    }
    
    printf("%lf", mult);

    return 0;
}