import std.experimental.all;

T read(T)() { return readln.chomp.to!T; }
T[] reads(T)() { return readln.split.to!(T[]); }
alias readint = read!int;
alias readints = reads!int;

int calc(int a, int b) {
    int x = (a + 2 * b) / 3;
    int y = (2 * a + b - 1) / 3;
    return x - y;
}

void main() {
    auto ab = readints;
    int a = ab[0], b = ab[1];

    auto ans = calc(a, b);
    writeln(ans);
}