while(numberOfRecurrence > 1000 || base > 35) { scanf("%d %d", numberOfRecurrence, base); } printf("%d%d", numberOfRecurrence, base); When input is 30 and 13, printed output is 0 and 0. What's the problem?

while(numberOfRecurrence > 1000 || base > 35) means that it will proceed only if (numberOfRecurrence > 1000 || base > 35) is true. Perhaps, initial value of numberOfRecurrence and base doesn't satisfy above condition so didn't run scanf statement at all. Maybe your intention was to use do-while statement.