View Compilation Error

0_0_25934880_11523.cpp: In function 'll extend_gcd(ll, ll, ll&, ll&, ll)':
0_0_25934880_11523.cpp:70:30: error: invalid initialization of non-const reference of type 'll& {aka long long int&}' from an rvalue of type 'll {aka long long int}'
     ll r = extend_gcd(b,a%b,y%M,x%M,M);
                              ^
0_0_25934880_11523.cpp:60:4: note: in passing argument 3 of 'll extend_gcd(ll, ll, ll&, ll&, ll)'
 ll extend_gcd(ll a,ll b,ll& x,ll &y, ll M)
    ^