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  1. #include <iostream>
  2. #include <iomanip>
  3. using namespace std;
  4.  
  5. int main() {
  6. double A,P,N;
  7. cin >> P >> N >> A;
  8. double res = (A-N)/(P-N)*1000;
  9. if (res >= 0 && P != N) cout <<fixed <<setprecision(1)<< res;
  10. else cout << -1;
  11. return 0;
  12. }
Success #stdin #stdout 0s 16064KB
stdin
50 30 30
stdout
0.0