C'de Hatamı Bulamıyorum

#include <cstdio>
#define MD 1000000007LL
typedef long long ll;
using namespace std;
typedef struct mtt{
    ll a[2][2];
}mt;
ll n;

mt mut(mt a,mt b){
    mt c={(a.a[0][0]*b.a[0][0]+a.a[0][1]*b.a[1][0])%MD,(a.a[0][0]*b.a[0][1]+a.a[0][1]*b.a[1][1])%MD,
    (a.a[1][0]*b.a[0][0]+a.a[1][1]*b.a[1][0])%MD,(a.a[1][0]*b.a[1][0]+a.a[1][1]*b.a[1][1])%MD};
    return c;
}

mt fp(mt a,ll k){
    mt a1={1,0,0,1};
    if(k==0)return a1;
    mt cc=fp(a,k/2);
    if(k%2)return mut(mut(cc,cc),a);
    else return mut(cc,cc);
}

ll f(ll n){
    mt a={1,1,1,0};
    mt c=fp(a,n);
    return c.a[0][0];

}

int main() {
    scanf("%lld",&n);
    n--;
    printf("%lld 
 ",f(n));
    return 0;}