void ford(int nod)
{
    int x, ps = 1, pi = 1;
    c[ps] = nod;
    while (ps <= pi) {
        viz[c[ps]] = 0;
        x = start[c[ps]];
        while (x) {
            if (cost[c[ps]] + a[2][x] < cost[a[0][x]]) {
                cost[a[0][x]] = cost[c[ps]] + a[2][x];
                if(viz[a[0][x]] == 0) {
                    viz[a[0][x]] = 1;
                    c[++pi] = a[0][x];
                }
            }
            x = a[1][x];
        }
        ps++;
    }
}