#include<stdio.h>
FILE *f=fopen("operatii.in","r"), *g=fopen("operatii.out","w");

long int n, px=0, x, nr=0, i, dif;

int main(){

    fscanf(f,"%ld\n",&n);
    for(i=1;i<=n;i++){
        fscanf(f,"%ld",&x);
        dif=x-px; if(dif>0){nr+=dif;}
        px=x;
    }   fprintf(g,"%ld",nr);

return 0;
}