Cod sursa(job #2463006)
Utilizator | Data | 28 septembrie 2019 10:25:04 | |
---|---|---|---|
Problema | Factorial | Scor | 60 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.51 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int n;
int f(int x) {
int ans = 0;
for (int i = 5; x / i >= 1; i *= 5) {
ans += x / i;
}
return ans;
}
int search_for(int cnt) {
int l = 1, r = 2e9, mid;
while(l <= r) {
mid = (l + r) / 2;
if (f(mid) < cnt) {
l = mid + 1;
}
else {
r = mid - 1;
}
}
if (f(mid) == cnt) return mid;
return -1;
}
int main() {
in >> n;
int ans = search_for(n);
return out << ans, 0;
}