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std::tuple<int, int, int> egcd(int a, int b){
if(a == 0) return {b, 0, 1};
int x, y, gcd;
std::tie(gcd, x, y) = egcd(b%a, a);
return {gcd, y - (b / a) * x, x};
}
int modinv(int a, int m){
int gcd, x, y;
std::tie(gcd, x, y) = egcd(a, m);
return (x%m + m) % m;
}

prog.cpp:1:6: error: ‘tuple’ in namespace ‘std’ does not name a template type
 std::tuple<int, int, int> egcd(int a, int b){
      ^~~~~
prog.cpp:1:1: note: ‘std::tuple’ is defined in header ‘<tuple>’; did you forget to ‘#include <tuple>’?
+#include <tuple>
 std::tuple<int, int, int> egcd(int a, int b){
 ^~~
prog.cpp: In function ‘int modinv(int, int)’:
prog.cpp:9:6: error: ‘tie’ is not a member of ‘std’
 std::tie(gcd, x, y) = egcd(a, m);
      ^~~
prog.cpp:9:23: error: ‘egcd’ was not declared in this scope
 std::tie(gcd, x, y) = egcd(a, m);
                       ^~~~
prog.cpp:9:23: note: suggested alternative: ‘gcd’
 std::tie(gcd, x, y) = egcd(a, m);
                       ^~~~
                       gcd

Standard output is empty