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| #include <bits/stdc++.h>
using namespace std;
const int N = 32;
int f[N][N], k, b, l, r, a[N];
int solve(int x) {
int ans = 0, tot = 0;
for (int i = 31; i; i--) {
if (x & (1 << i)) {
tot++;
if (tot > k) break;
x ^= (1 << i);
}
if (x >= (1 << (i - 1))) ans += f[i - 1][k - tot];
}
if (tot + x == k) ans++;
return ans;
}
int calc(int x, int b) {
int cnt = 0;
while (x) {
a[cnt++] = x % b;
x /= b;
}
int res = 0;
for (int i = cnt - 1; i + 1; i--) {
if (a[i] > 1) {
for (int j = i; j + 1; j--) res |= (1 << j);
} else res |= (a[i] << i);
}
return res;
}
int main() {
scanf("%d %d %d %d", &l, &r, &k, &b);
f[0][0] = 1;
for (int i = 1; i < N; i++) {
f[i][0] = 1;
for (int j = 1; j <= i; j++) f[i][j] = f[i - 1][j] + f[i - 1][j - 1];
}
printf("%d\n", solve(calc(r, b)) - solve(calc(l - 1, b)));
return 0;
}
|