خطای not all control path return a value بر طرفش کنم

}
//+------------------------------------------------------------------+
//| GetCurrencyIndex(string currency) |
//+------------------------------------------------------------------+
int GetCurrencyIndex(string currency)
{
for (int i = 0; i < CURRENCYCOUNT; i++)
{
if (currencyNames[i] == currency)
{
return(i);
}
}
return (-1);
}