#include <iostream>
#include <math.h>
using namespace std;
int factorial(int param) {
int fact = 1;
for(int i = 2; i <= param; i++)
fact = fact*i;
return fact;
}
int main() {
double sum = 0;
int n, x;
n = 3; // cin >> n;
x = 5; // cin >> 5;
for(int i = 1; i <= n; i++) {
sum = sum + pow(x, i)/factorial(i);
}
cout << sum;
return 0;
}
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