Let $\overbrace{75 \ldots . .57}^r$ denote the $(r+2)$ digit number where the first and the last digits are 7 and the remaining $r$ digits are 5. Consider the sum $\mathrm{S}=77+757+7557+\ldots \ldots+\overbrace{75 \ldots . .57}^{98}$. If $\mathrm{S}=\frac{\overbrace{75 \ldots . .57}^{99}+\mathrm{m}}{\mathrm{n}}$, where $m$ and $n$ are natural numbers less than 3000 , then the value of $m+n$ is