#include <stdio.h>

int main() {
    int n;
    int a=1, b=1, c=1, d=0;  // Fibonacci Q-matrix [[1,1],[1,0]]
    int res_a=1, res_b=0, res_c=0, res_d=1; // Identity matrix
    int x,y,z,w;

    printf("Enter n: ");
    scanf("%d", &n);


    while(n > 0) {
        if(n & 1) { // res = res * base
            x = res_a*a + res_b*c;
            y = res_a*b + res_b*d;
            z = res_c*a + res_d*c;
            w = res_c*b + res_d*d;
            res_a=x; res_b=y; res_c=z; res_d=w;
        }

        // base = base * base
        x = a*a + b*c;
        y = a*b + b*d;
        z = c*a + d*c;
        w = c*b + d*d;
        a=x; b=y; c=z; d=w;

        n >>= 1; // divide by 2
    }

    printf("Fibonacci = %d\n", res_b);  // F(n) is stored here
    return 0;
}