#include <cstdio>
int v, h, i, j, k;
double l, r, x[1<<21], y[1<<21];
bool flag;
int main() {
    freopen("sars.in","r",stdin);
    freopen("sars.out","w",stdout);
    scanf("%lf %lf %lf %d", x, &r, &l, &v);
    l *= 2;
    r += 0.00001;
    x[1] = x[0];
    while(l > 1) {
        i++;
        h += v;
        l /= 2;
        flag = false;
        for(j=1; j<=(1<<(i-1)); j++) {
            //区间[x[j]-r, x[j]+r] 交 区间[h-v, h] 不等于 空
            if((x[j]+r > h-v && x[j]+r < h) || (x[j]+r > h && x[j]-r < h))
                flag = true;
            y[j*2-1] = x[j] - l;
            y[j*2] = x[j] + l;
        }
        if(flag)
            k++;
        for(j=1; j<=(1<<i); j++)
            x[j] = y[j];
    };
    printf("%d\n", k);
    return 0;
}