#include <bits/stdc++.h>
using namespace std;
int n;
bool first = true;
void print(long long x)
{
    if (first) {
        first = false;
        cout << "=";
    } else {
        cout << "*";
    }
    cout << x;
}
int main(){
    long long a = 1, b = 1, c, n;
    cin >> n;
    for (int i = 3; i <= n; i++) {
        c = (a + b) % (1 << 31);
        a = b;
        b = c;
    }
    cout << c;
    for (int i = 2; i * i <= c; i++) {
        if (c % i == 0) {
            while (c % i == 0) {
                c /= i;
                print(i);
            }
        }
    }
    if (c > 1)
        print(c);
    return 0;
}

首先用递推求出f(n)，然后分解质因数即可。需要注意输出格式，可以用一个变量first表示当前输入的是否是第一个质因数，并分情况处理。

long long a = 1, b = 1, c, n;
cin >> n;
for (int i = 3; i <= n; i++) {
    c = (a + b) % (1 << 31);
    a = b;
    b = c;
}
cout << c;
for (int i = 2; i * i <= c; i++) {
    if (c % i == 0) {
        while (c % i == 0) {
            c /= i;
            print(i);
        }
    }
}
if (c > 1)
    print(c);

bool first = true;
void print(long long x)
{
    if (first) {
        first = false;
        cout << "=";
    } else {
        cout << "*";
    }
    cout << x;
}