POJ 2661 Factstone Benchmark

#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int main() {
	int y, i;
	double w;
	while (scanf("%d", &y) && y) {
		w = log(4 * 1.0);
		for (int j = 1960; j <= y; j += 10) {
			w *= 2;
		}
		i = 1;
		double f = 0;
		while (f < w) {
			f += log((double)++i * 1.0);
		}
		printf("%d\n", i - 1);
	}
}

使用對數就好