#include <stdio.h>
#include <stdlib.h>
 
double monte_carlo_e(int n) {
    int count = 0;
    for (int i = 0; i < n; i++) {
        double sum = 0.0;
        int k = 0;
        while (sum < 1.0) {
            sum += (double)rand() / RAND_MAX;
            k++;
        }
        count += k;
    }
    return (double)count / n;
}
 
int main() {
    int n = 1000000; // 試行回数
    double e_approx = monte_carlo_e(n);
    printf("%f\n", e_approx);
    return 0;
}

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