#include <stdio.h>

int min(int a, int b) {
    return a < b ? a : b;
}

int solution(int mainTank, int additionalTank) {
    int total_fuel_used = 0;
    int current_main = mainTank;
    int current_additional = additionalTank;
    
    while (current_main > 0) {
        // Use fuel in chunks of 5 liters or whatever is left
        int fuel_to_use = min(5, current_main);
        current_main -= fuel_to_use;
        total_fuel_used += fuel_to_use;
        
        // If we used exactly 5 liters and have additional fuel, transfer 1 liter
        if (fuel_to_use == 5 && current_additional > 0) {
            current_main += 1;
            current_additional -= 1;
        }
    }
    
    // Distance is fuel used * 10 km per liter
    int distance = total_fuel_used * 10;
    
    return distance;
}

int main() {
    int mainTank, additionalTank;
    scanf("%d", &mainTank);
    scanf("%d", &additionalTank);
    int result = solution(mainTank, additionalTank);
    printf("%d\n", result);
    return 0;
}